This was done entirely with mindless brute force, using
git grep -l '\<k[vmz]*alloc_objs*(.*, GFP_KERNEL)' |
xargs sed -i 's/\(alloc_objs*(.*\), GFP_KERNEL)/\1)/'
to convert the new alloc_obj() users that had a simple GFP_KERNEL
argument to just drop that argument.
Note that due to the extreme simplicity of the scripting, any slightly
more complex cases spread over multiple lines would not be triggered:
they definitely exist, but this covers the vast bulk of the cases, and
the resulting diff is also then easier to check automatically.
For the same reason the 'flex' versions will be done as a separate
conversion.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:
Single allocations: kmalloc(sizeof(TYPE), ...)
are replaced with: kmalloc_obj(TYPE, ...)
Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with: kmalloc_objs(TYPE, COUNT, ...)
Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...)
(where TYPE may also be *VAR)
The resulting allocations no longer return "void *", instead returning
"TYPE *".
Signed-off-by: Kees Cook <kees@kernel.org>
do_con_write(), fbcon_redraw.*() invoke console_conditional_schedule()
which is a conditional scheduling point based on printk's internal
variables console_may_schedule. It may only be used if the console lock
is acquired for instance via console_lock() or console_trylock().
Prinkt sets the internal variable to 1 (and allows to schedule)
if the console lock has been acquired via console_lock(). The trylock
does not allow it.
The console_conditional_schedule() invocation in do_con_write() is
invoked shortly before console_unlock().
The console_conditional_schedule() invocation in fbcon_redraw.*()
original from fbcon_scroll() / vt's con_scroll() which originate from a
line feed.
In console_unlock() the variable is set to 0 (forbids to schedule) and
it tries to schedule while making progress printing. This is brand new
compared to when console_conditional_schedule() was added in v2.4.9.11.
In v2.6.38-rc3, console_unlock() (started its existence) iterated over
all consoles and flushed them with disabled interrupts. A scheduling
attempt here was not possible, it relied that a long print scheduled
before console_unlock().
Since commit 8d91f8b153 ("printk: do cond_resched() between lines
while outputting to consoles"), which appeared in v4.5-rc1,
console_unlock() attempts to schedule if it was allowed to schedule
while during console_lock(). Each record is idealy one line so after
every line feed.
This console_conditional_schedule() is also only relevant on
PREEMPT_NONE and PREEMPT_VOLUNTARY builds. In other configurations
cond_resched() becomes a nop and has no impact.
I'm bringing this all up just proof that it is not required anymore. It
becomes a problem on a PREEMPT_RT build with debug code enabled because
that might_sleep() in cond_resched() remains and triggers a warnings.
This is due to
legacy_kthread_func-> console_flush_one_record -> vt_console_print-> lf
-> con_scroll -> fbcon_scroll
and vt_console_print() acquires a spinlock_t which does not allow a
voluntary schedule. There is no need to fb_scroll() to schedule since
console_flush_one_record() attempts to schedule after each line.
!PREEMPT_RT is not affected because the legacy printing thread is only
enabled on PREEMPT_RT builds.
Therefore I suggest to remove console_conditional_schedule().
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Helge Deller <deller@gmx.de>
Cc: linux-fbdev@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Fixes: 5f53ca3ff8 ("printk: Implement legacy printer kthread for PREEMPT_RT")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Petr Mladek <pmladek@suse.com> # from printk() POV
Signed-off-by: Helge Deller <deller@gmx.de>
Pull networking updates from Paolo Abeni:
"Core & protocols:
- A significant effort all around the stack to guide the compiler to
make the right choice when inlining code, to avoid unneeded calls
for small helper and stack canary overhead in the fast-path.
This generates better and faster code with very small or no text
size increases, as in many cases the call generated more code than
the actual inlined helper.
- Extend AccECN implementation so that is now functionally complete,
also allow the user-space enabling it on a per network namespace
basis.
- Add support for memory providers with large (above 4K) rx buffer.
Paired with hw-gro, larger rx buffer sizes reduce the number of
buffers traversing the stack, dincreasing single stream CPU usage
by up to ~30%.
- Do not add HBH header to Big TCP GSO packets. This simplifies the
RX path, the TX path and the NIC drivers, and is possible because
user-space taps can now interpret correctly such packets without
the HBH hint.
- Allow IPv6 routes to be configured with a gateway address that is
resolved out of a different interface than the one specified,
aligning IPv6 to IPv4 behavior.
- Multi-queue aware sch_cake. This makes it possible to scale the
rate shaper of sch_cake across multiple CPUs, while still enforcing
a single global rate on the interface.
- Add support for the nbcon (new buffer console) infrastructure to
netconsole, enabling lock-free, priority-based console operations
that are safer in crash scenarios.
- Improve the TCP ipv6 output path to cache the flow information,
saving cpu cycles, reducing cache line misses and stack use.
- Improve netfilter packet tracker to resolve clashes for most
protocols, avoiding unneeded drops on rare occasions.
- Add IP6IP6 tunneling acceleration to the flowtable infrastructure.
- Reduce tcp socket size by one cache line.
- Notify neighbour changes atomically, avoiding inconsistencies
between the notification sequence and the actual states sequence.
- Add vsock namespace support, allowing complete isolation of vsocks
across different network namespaces.
- Improve xsk generic performances with cache-alignment-oriented
optimizations.
- Support netconsole automatic target recovery, allowing netconsole
to reestablish targets when underlying low-level interface comes
back online.
Driver API:
- Support for switching the working mode (automatic vs manual) of a
DPLL device via netlink.
- Introduce PHY ports representation to expose multiple front-facing
media ports over a single MAC.
- Introduce "rx-polarity" and "tx-polarity" device tree properties,
to generalize polarity inversion requirements for differential
signaling.
- Add helper to create, prepare and enable managed clocks.
Device drivers:
- Add Huawei hinic3 PF etherner driver.
- Add DWMAC glue driver for Motorcomm YT6801 PCIe ethernet
controller.
- Add ethernet driver for MaxLinear MxL862xx switches
- Remove parallel-port Ethernet driver.
- Convert existing driver timestamp configuration reporting to
hwtstamp_get and remove legacy ioctl().
- Convert existing drivers to .get_rx_ring_count(), simplifing the RX
ring count retrieval. Also remove the legacy fallback path.
- Ethernet high-speed NICs:
- Broadcom (bnxt, bng):
- bnxt: add FW interface update to support FEC stats histogram
and NVRAM defragmentation
- bng: add TSO and H/W GRO support
- nVidia/Mellanox (mlx5):
- improve latency of channel restart operations, reducing the
used H/W resources
- add TSO support for UDP over GRE over VLAN
- add flow counters support for hardware steering (HWS) rules
- use a static memory area to store headers for H/W GRO,
leading to 12% RX tput improvement
- Intel (100G, ice, idpf):
- ice: reorganizes layout of Tx and Rx rings for cacheline
locality and utilizes __cacheline_group* macros on the new
layouts
- ice: introduces Synchronous Ethernet (SyncE) support
- Meta (fbnic):
- adds debugfs for firmware mailbox and tx/rx rings vectors
- Ethernet virtual:
- geneve: introduce GRO/GSO support for double UDP encapsulation
- Ethernet NICs consumer, and embedded:
- Synopsys (stmmac):
- some code refactoring and cleanups
- RealTek (r8169):
- add support for RTL8127ATF (10G Fiber SFP)
- add dash and LTR support
- Airoha:
- AN8811HB 2.5 Gbps phy support
- Freescale (fec):
- add XDP zero-copy support
- Thunderbolt:
- add get link setting support to allow bonding
- Renesas:
- add support for RZ/G3L GBETH SoC
- Ethernet switches:
- Maxlinear:
- support R(G)MII slow rate configuration
- add support for Intel GSW150
- Motorcomm (yt921x):
- add DCB/QoS support
- TI:
- icssm-prueth: support bridging (STP/RSTP) via the switchdev
framework
- Ethernet PHYs:
- Realtek:
- enable SGMII and 2500Base-X in-band auto-negotiation
- simplify and reunify C22/C45 drivers
- Micrel: convert bindings to DT schema
- CAN:
- move skb headroom content into skb extensions, making CAN
metadata access more robust
- CAN drivers:
- rcar_canfd:
- add support for FD-only mode
- add support for the RZ/T2H SoC
- sja1000: cleanup the CAN state handling
- WiFi:
- implement EPPKE/802.1X over auth frames support
- split up drop reasons better, removing generic RX_DROP
- additional FTM capabilities: 6 GHz support, supported number of
spatial streams and supported number of LTF repetitions
- better mac80211 iterators to enumerate resources
- initial UHR (Wi-Fi 8) support for cfg80211/mac80211
- WiFi drivers:
- Qualcomm/Atheros:
- ath11k: support for Channel Frequency Response measurement
- ath12k: a significant driver refactor to support multi-wiphy
devices and and pave the way for future device support in the
same driver (rather than splitting to ath13k)
- ath12k: support for the QCC2072 chipset
- Intel:
- iwlwifi: partial Neighbor Awareness Networking (NAN) support
- iwlwifi: initial support for U-NII-9 and IEEE 802.11bn
- RealTek (rtw89):
- preparations for RTL8922DE support
- Bluetooth:
- implement setsockopt(BT_PHY) to set the connection packet type/PHY
- set link_policy on incoming ACL connections
- Bluetooth drivers:
- btusb: add support for MediaTek7920, Realtek RTL8761BU and 8851BE
- btqca: add WCN6855 firmware priority selection feature"
* tag 'net-next-7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1254 commits)
bnge/bng_re: Add a new HSI
net: macb: Fix tx/rx malfunction after phy link down and up
af_unix: Fix memleak of newsk in unix_stream_connect().
net: ti: icssg-prueth: Add optional dependency on HSR
net: dsa: add basic initial driver for MxL862xx switches
net: mdio: add unlocked mdiodev C45 bus accessors
net: dsa: add tag format for MxL862xx switches
dt-bindings: net: dsa: add MaxLinear MxL862xx
selftests: drivers: net: hw: Modify toeplitz.c to poll for packets
octeontx2-pf: Unregister devlink on probe failure
net: renesas: rswitch: fix forwarding offload statemachine
ionic: Rate limit unknown xcvr type messages
tcp: inet6_csk_xmit() optimization
tcp: populate inet->cork.fl.u.ip6 in tcp_v6_syn_recv_sock()
tcp: populate inet->cork.fl.u.ip6 in tcp_v6_connect()
ipv6: inet6_csk_xmit() and inet6_csk_update_pmtu() use inet->cork.fl.u.ip6
ipv6: use inet->cork.fl.u.ip6 and np->final in ip6_datagram_dst_update()
ipv6: use np->final in inet6_sk_rebuild_header()
ipv6: add daddr/final storage in struct ipv6_pinfo
net: stmmac: qcom-ethqos: fix qcom_ethqos_serdes_powerup()
...
Extend struct printk_info to include the task name, pid, and CPU
number where printk messages originate. This information is captured
at vprintk_store() time and propagated through printk_message to
nbcon_write_context, making it available to nbcon console drivers.
This is useful for consoles like netconsole that want to include
execution context in their output, allowing correlation of messages
with specific tasks and CPUs regardless of where the console driver
actually runs.
The feature is controlled by CONFIG_PRINTK_EXECUTION_CTX, which is
automatically selected by CONFIG_NETCONSOLE_DYNAMIC. When disabled,
the helper functions compile to no-ops with no overhead.
Suggested-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Link: https://patch.msgid.link/20260206-nbcon-v7-1-62bda69b1b41@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
With Sparse support gone, Clang is a bit more strict and warns:
./include/linux/console.h:492:50: error: use of undeclared identifier 'console_mutex'
492 | extern void console_list_unlock(void) __releases(console_mutex);
Since it does not make sense to make console_mutex itself global, move
the annotation to printk.c. Context analysis remains disabled for
printk.c.
This is needed to enable context analysis for modules that include
<linux/console.h>.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251219154418.3592607-34-elver@google.com
Pull SoC driver updates from Arnd Bergmann:
"This is the first half of the driver changes:
- A treewide interface change to the "syscore" operations for power
management, as a preparation for future Tegra specific changes
- Reset controller updates with added drivers for LAN969x, eic770 and
RZ/G3S SoCs
- Protection of system controller registers on Renesas and Google
SoCs, to prevent trivially triggering a system crash from e.g.
debugfs access
- soc_device identification updates on Nvidia, Exynos and Mediatek
- debugfs support in the ST STM32 firewall driver
- Minor updates for SoC drivers on AMD/Xilinx, Renesas, Allwinner, TI
- Cleanups for memory controller support on Nvidia and Renesas"
* tag 'soc-drivers-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc: (114 commits)
memory: tegra186-emc: Fix missing put_bpmp
Documentation: reset: Remove reset_controller_add_lookup()
reset: fix BIT macro reference
reset: rzg2l-usbphy-ctrl: Fix a NULL vs IS_ERR() bug in probe
reset: th1520: Support reset controllers in more subsystems
reset: th1520: Prepare for supporting multiple controllers
dt-bindings: reset: thead,th1520-reset: Add controllers for more subsys
dt-bindings: reset: thead,th1520-reset: Remove non-VO-subsystem resets
reset: remove legacy reset lookup code
clk: davinci: psc: drop unused reset lookup
reset: rzg2l-usbphy-ctrl: Add support for RZ/G3S SoC
reset: rzg2l-usbphy-ctrl: Add support for USB PWRRDY
dt-bindings: reset: renesas,rzg2l-usbphy-ctrl: Document RZ/G3S support
reset: eswin: Add eic7700 reset driver
dt-bindings: reset: eswin: Documentation for eic7700 SoC
reset: sparx5: add LAN969x support
dt-bindings: reset: microchip: Add LAN969x support
soc: rockchip: grf: Add select correct PWM implementation on RK3368
soc/tegra: pmc: Add USB wake events for Tegra234
amba: tegra-ahb: Fix device leak on SMMU enable
...
The macro for_each_console_srcu iterates over all registered consoles. It's
implied that all registered consoles have CON_ENABLED flag set, making
the check for the flag unnecessary. Call console_is_usable function to
fully verify if the given console is usable before calling the ->unblank
callback.
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://patch.msgid.link/20251121-printk-cleanup-part2-v2-3-57b8b78647f4@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
With commit ("printk: Avoid scheduling irq_work on suspend") the
implementation of printk_get_console_flush_type() was modified to
avoid offloading when irq_work should be blocked during suspend.
Since printk uses the returned flush type to determine what
flushing methods are used, this was thought to be sufficient for
avoiding irq_work usage during the suspend phase.
However, vprintk_emit() implements a hack to support
printk_deferred(). In this hack, the returned flush type is
adjusted to make sure no legacy direct printing occurs when
printk_deferred() was used.
Because of this hack, the legacy offloading flushing method can
still be used, causing irq_work to be queued when it should not
be.
Adjust the vprintk_emit() hack to also consider
@console_irqwork_blocked so that legacy offloading will not be
chosen when irq_work should be blocked.
Link: https://lore.kernel.org/lkml/87fra90xv4.fsf@jogness.linutronix.de
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Fixes: 26873e3e7f ("printk: Avoid scheduling irq_work on suspend")
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Allowing irq_work to be scheduled while trying to suspend has shown
to cause problems as some architectures interpret the pending
interrupts as a reason to not suspend. This became a problem for
printk() with the introduction of NBCON consoles. With every
printk() call, NBCON console printing kthreads are woken by queueing
irq_work. This means that irq_work continues to be queued due to
printk() calls late in the suspend procedure.
Avoid this problem by preventing printk() from queueing irq_work
once console suspending has begun. This applies to triggering NBCON
and legacy deferred printing as well as klogd waiters.
Since triggering of NBCON threaded printing relies on irq_work, the
pr_flush() within console_suspend_all() is used to perform the final
flushing before suspending consoles and blocking irq_work queueing.
NBCON consoles that are not suspended (due to the usage of the
"no_console_suspend" boot argument) transition to atomic flushing.
Introduce a new global variable @console_irqwork_blocked to flag
when irq_work queueing is to be avoided. The flag is used by
printk_get_console_flush_type() to avoid allowing deferred printing
and switch NBCON consoles to atomic flushing. It is also used by
vprintk_emit() to avoid klogd waking.
Add WARN_ON_ONCE(console_irqwork_blocked) to the irq_work queuing
functions to catch any code that attempts to queue printk irq_work
during the suspending/resuming procedure.
Cc: stable@vger.kernel.org # 6.13.x because no drivers in 6.12.x
Fixes: 6b93bb41f6 ("printk: Add non-BKL (nbcon) console basic infrastructure")
Closes: https://lore.kernel.org/lkml/DB9PR04MB8429E7DDF2D93C2695DE401D92C4A@DB9PR04MB8429.eurprd04.prod.outlook.com
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Sherry Sun <sherry.sun@nxp.com>
Link: https://patch.msgid.link/20251113160351.113031-3-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
Several drivers can benefit from registering per-instance data along
with the syscore operations. To achieve this, move the modifiable fields
out of the syscore_ops structure and into a separate struct syscore that
can be registered with the framework. Add a void * driver data field for
drivers to store contextual data that will be passed to the syscore ops.
Acked-by: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
printk_legacy_map is used to hide lock nesting violations caused by
legacy drivers and is using the wrong override type. LD_WAIT_SLEEP is
for always sleeping lock types such as mutex_t. LD_WAIT_CONFIG is for
lock type which are sleeping while spinning on PREEMPT_RT such as
spinlock_t.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20251026150726.GA23223@redhat.com
[pmladek@suse.com: Fixed indentation.]
Signed-off-by: Petr Mladek <pmladek@suse.com>
The legacy printer kthread uses console_lock and
__console_flush_and_unlock to flush records to the console. This
approach results in the console_lock being held for the entire
duration of a flush. This can result in large waiting times for
those waiting for console_lock especially where there is a large
volume of records or where the console is slow (e.g. serial). This
contention is observed during boot, as the call to filp_open in
console_on_rootfs will delay progression to userspace until any
in-flight flush is completed.
Let's instead use console_flush_one_record and release/reacquire
the console_lock between records.
On a PocketBeagle 2, with the following boot args:
"console=ttyS2,9600 initcall_debug=1 loglevel=10"
Without this patch:
[ 5.613166] +console_on_rootfs/filp_open
[ 5.643473] mmc1: SDHCI controller on fa00000.mmc [fa00000.mmc] using ADMA 64-bit
[ 5.643823] probe of fa00000.mmc returned 0 after 258244 usecs
[ 5.710520] mmc1: new UHS-I speed SDR104 SDHC card at address 5048
[ 5.721976] mmcblk1: mmc1:5048 SD32G 29.7 GiB
[ 5.747258] mmcblk1: p1 p2
[ 5.753324] probe of mmc1:5048 returned 0 after 40002 usecs
[ 15.595240] ti_sci_pm_domains 44043000.system-controller:power-controller: sync_state() pending due to 30040000.pruss
[ 15.595282] ti_sci_pm_domains 44043000.system-controller:power-controller: sync_state() pending due to e010000.watchdog
[ 15.595297] ti_sci_pm_domains 44043000.system-controller:power-controller: sync_state() pending due to e000000.watchdog
[ 15.595437] ti_sci_pm_domains 44043000.system-controller:power-controller: sync_state() pending due to 30300000.crc
[ 146.275961] -console_on_rootfs/filp_open ...
and with:
[ 5.477122] +console_on_rootfs/filp_open
[ 5.595814] mmc1: SDHCI controller on fa00000.mmc [fa00000.mmc] using ADMA 64-bit
[ 5.596181] probe of fa00000.mmc returned 0 after 312757 usecs
[ 5.662813] mmc1: new UHS-I speed SDR104 SDHC card at address 5048
[ 5.674367] mmcblk1: mmc1:5048 SD32G 29.7 GiB
[ 5.699320] mmcblk1: p1 p2
[ 5.705494] probe of mmc1:5048 returned 0 after 39987 usecs
[ 6.418682] -console_on_rootfs/filp_open ...
...
[ 15.593509] ti_sci_pm_domains 44043000.system-controller:power-controller: sync_state() pending due to 30040000.pruss
[ 15.593551] ti_sci_pm_domains 44043000.system-controller:power-controller: sync_state() pending due to e010000.watchdog
[ 15.593566] ti_sci_pm_domains 44043000.system-controller:power-controller: sync_state() pending due to e000000.watchdog
[ 15.593704] ti_sci_pm_domains 44043000.system-controller:power-controller: sync_state() pending due to 30300000.crc
Where I've added a printk surrounding the call in console_on_rootfs
to filp_open.
Suggested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Andrew Murray <amurray@thegoodpenguin.co.uk>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Link: https://patch.msgid.link/20251020-printk_legacy_thread_console_lock-v3-3-00f1f0ac055a@thegoodpenguin.co.uk
[pmladek@suse.com: Fixed ordering of variable definition suggested by John.]
Signed-off-by: Petr Mladek <pmladek@suse.com>
console_flush_one_record() and console_flush_all() duplicate several
checks. They both want to tell the caller that consoles are not
longer usable in this context because it has lost the lock or
the lock has to be reserved for the panic CPU.
Remove the duplication by changing the semantic of the function
console_flush_one_record() return value and parameters.
The function will return true when it is able to do the job. It means
that there is at least one usable console. And the flushing was
not interrupted by a takeover or panic_on_other_cpu().
Also replace the @any_usable parameter with @try_again. The @try_again
parameter will be set to true when the function could do the job
and at least one console made a progress.
Motivation:
The callers need to know when
+ they should continue flushing => @try_again
+ when the console is flushed => can_do_the_job(return) && !@try_again
+ when @next_seq is valid => same as flushed
+ when lost console_lock => @takeover
The proposed change makes it clear when the function can do
the job. It simplifies the answer for the other questions.
Also the return value from console_flush_one_record() can
be used as return value from console_flush_all().
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Link: https://patch.msgid.link/20251020-printk_legacy_thread_console_lock-v3-2-00f1f0ac055a@thegoodpenguin.co.uk
[pmladek@suse.com: Fixed type of any_usable variable reported by John]
Signed-off-by: Petr Mladek <pmladek@suse.com>
console_flush_all prints all remaining records to all usable consoles
whilst its caller holds console_lock. This can result in large waiting
times for those waiting for console_lock especially where there is a
large volume of records or where the console is slow (e.g. serial).
Let's extract the parts of this function which print a single record
into a new function named console_flush_one_record. This can later
be used for functions that will release and reacquire console_lock
between records.
This commit should not change existing functionality.
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Andrew Murray <amurray@thegoodpenguin.co.uk>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Link: https://patch.msgid.link/20251020-printk_legacy_thread_console_lock-v3-1-00f1f0ac055a@thegoodpenguin.co.uk
Signed-off-by: Petr Mladek <pmladek@suse.com>
The kthreads for nbcon consoles are created by nbcon_alloc() at
the beginning of the console registration. But it currently works
only for the 2nd or later nbcon console because the code checks
@printk_kthreads_running.
The kthread for the 1st registered nbcon console is created at the very
end of register_console() by printk_kthreads_check_locked(). As a result,
the entire log is replayed synchronously when the "enabled" message
gets printed. It might block the boot for a long time with a slow serial
console.
Prevent the synchronous flush by creating the kthread even for the 1st
nbcon console when it is safe (kthreads ready and no boot consoles).
Also inform printk() to use the kthread by setting
@printk_kthreads_running. Note that the kthreads already must be
running when it is safe and this is not the 1st nbcon console.
Symmetrically, clear @printk_kthreads_running when the last nbcon
console was unregistered by nbcon_free(). This requires updating
@have_nbcon_console before nbcon_free() gets called.
Note that there is _no_ problem when the 1st nbcon console replaces boot
consoles. In this case, the kthread will be started at the end
of registration after the boot consoles are removed. But the console
does not reply the entire log buffer in this case. Note that
the flag CON_PRINTBUFFER is always cleared when the boot consoles are
removed and vice versa.
Closes: https://lore.kernel.org/r/20250514173514.2117832-1-mcobb@thegoodpenguin.co.uk
Tested-by: Michael Cobb <mcobb@thegoodpenguin.co.uk>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Link: https://patch.msgid.link/20250604142045.253301-1-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Pull printk updates from Petr Mladek:
- New option "printk.debug_non_panic_cpus" allows to store printk
messages from non-panic CPUs during panic. It might be useful when
panic() fails. It is disabled by default because it increases the
chance to see the messages printed before panic() and on the
panic-CPU.
- New build option "CONFIG_NULL_TTY_DEFAULT_CONSOLE" allows to build
kernel without the virtual terminal support which prefers ttynull
over serial console.
- Do not unblank suspended consoles.
- Some code clean up.
* tag 'printk-for-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
printk/panic: Add option to allow non-panic CPUs to write to the ring buffer.
printk: Add an option to allow ttynull to be a default console device
printk: Check CON_SUSPEND when unblanking a console
printk: Rename console_start to console_resume
printk: Rename console_stop to console_suspend
printk: Rename resume_console to console_resume_all
printk: Rename suspend_console to console_suspend_all
Commit 779dbc2e78 ("printk: Avoid non-panic CPUs writing to ringbuffer")
aimed to isolate panic-related messages. However, when panic() itself
malfunctions, messages from non-panic CPUs become crucial for debugging.
While commit bcc954c6ca ("printk/panic: Allow cpu backtraces to
be written into ringbuffer during panic") enables non-panic CPU
backtraces, it may not provide sufficient diagnostic information.
Introduce the "debug_non_panic_cpus" command-line option, enabling
non-panic CPU messages to be stored in the ring buffer during a panic.
This also prevents discarding non-finalized messages from non-panic CPUs
during console flushing, providing a more comprehensive view of system
state during critical failures.
Link: https://lore.kernel.org/all/Z8cLEkqLL2IOyNIj@pathway/
Signed-off-by: Donghyeok Choe <d7271.choe@samsung.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20250318022320.2428155-1-d7271.choe@samsung.com
[pmladek@suse.com: Added documentation, added module_parameter, removed printk_ prefix.]
Tested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
The new option is CONFIG_NULL_TTY_DEFAULT_CONSOLE.
if enabled, and CONFIG_VT is disabled, ttynull will become the default
primary console device.
ttynull will be the only console device usually with this option enabled.
Some architectures do call add_preferred_console() which may add another
console though.
Motivation:
Many distributions ship with CONFIG_VT enabled. On tested desktop hardware
if CONFIG_VT is disabled, the default console device falls back to
/dev/ttyS0 instead of /dev/tty.
This could cause issues in user space, and hardware problems:
1. The user space issues include the case where /dev/ttyS0 is
disconnected, and the TCGETS ioctl, which some user space libraries use
as a probe to determine if a file is a tty, is called on /dev/console and
fails. Programs that call isatty() on /dev/console and get an incorrect
false value may skip expected logging to /dev/console.
2. The hardware issues include the case if a user has a science instrument
or other device connected to the /dev/ttyS0 port, and they were to upgrade
to a kernel that is disabling the CONFIG_VT option, kernel logs will then
be sent to the device connected to /dev/ttyS0 unless they edit their
kernel command line manually.
The new CONFIG_NULL_TTY_DEFAULT_CONSOLE option will give users and
distribution maintainers an option to avoid this. Disabling CONFIG_VT and
enabling CONFIG_NULL_TTY_DEFAULT_CONSOLE will ensure the default kernel
console behavior is not dependent on hardware configuration by default, and
avoid unexpected new behavior on devices connected to the /dev/ttyS0 serial
port.
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Adam Simonelli <adamsimonelli@gmail.com>
Link: https://lore.kernel.org/r/20250314160749.3286153-2-adamsimonelli@gmail.com
[pmladek@suse.com: Fixed indentation of the commit message.]
Signed-off-by: Petr Mladek <pmladek@suse.com>
The documentation of printk_cpu_sync_get() clearly states
that the owner must never perform any activities where it waits
for a CPU. For legacy printing there can be spinning on the
console_lock and on the port lock. Therefore legacy printing
must be deferred when holding the printk_cpu_sync.
Note that in the case of emergency states, atomic consoles
are not prevented from printing when printk is deferred. This
is appropriate because they do not spin-wait indefinitely for
other CPUs.
Reported-by: Rik van Riel <riel@surriel.com>
Closes: https://lore.kernel.org/r/20240715232052.73eb7fb1@imladris.surriel.com
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Fixes: 55d6af1d66 ("lib/nmi_backtrace: explicitly serialize banner and regs")
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20241209111746.192559-3-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
Shifting 1 << 31 on a 32-bit int causes signed integer overflow, which
leads to undefined behavior. To prevent this, cast 1 to u32 before
performing the shift, ensuring well-defined behavior.
This change explicitly avoids any potential overflow by ensuring that
the shift occurs on an unsigned 32-bit integer.
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Acked-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240928113608.1438087-1-visitorckw@gmail.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Pull printk updates from Petr Mladek:
- Print more precise information about the printk log buffer memory
usage.
- Make sure that the sysrq title is shown on the console even when
deferred.
- Do not enable earlycon by `console=` which is meant to disable the
default console.
* tag 'printk-for-6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
printk: add dummy printk_force_console_enter/exit helpers
tty: sysrq: Use printk_force_console context on __handle_sysrq
printk: Introduce FORCE_CON flag
printk: Improve memory usage logging during boot
init: Don't proxy `console=` to earlycon
Introduce FORCE_CON flag to printk. The new flag will make it possible to
create a context where printk messages will never be suppressed.
This mechanism will be used in the next patch to create a force_con
context on sysrq handling, removing an existing workaround on the
loglevel global variable. The workaround existed to make sure that sysrq
header messages were sent to all consoles, but this doesn't work with
deferred messages because the loglevel might be restored to its original
value before a console flushes the messages.
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20241105-printk-loud-con-v2-1-bd3ecdf7b0e4@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
When the initial printk ring buffer size is updated, setup_log_buf()
allocates a new ring buffer, as well as a set of meta-data structures
for the new ring buffer. The function also emits the new size of the
ring buffer, but not the size of the meta-data structures.
This makes it difficult to assess how changing the log buffer size
impacts memory usage during boot.
For instance, increasing the ring buffer size from 512 KB to 1 MB
through the command line yields an increase of 2304 KB in reserved
memory at boot, while the only obvious change is the 512 KB
difference in the ring buffer sizes:
log_buf_len=512K:
printk: log_buf_len: 524288 bytes
Memory: ... (... 733252K reserved ...)
log_buf_len=1M:
printk: log_buf_len: 1048576 bytes
Memory: ... (... 735556K reserved ...)
This is because of how the size of the meta-data structures scale with
the size of the ring buffer.
Even when there aren't changes to the printk ring buffer size (i.e. the
initial size == 1 << CONFIG_LOG_BUF_SHIFT), it is impossible to tell
how much memory is consumed by the printk ring buffer during boot.
Therefore, unconditionally log the sizes of the printk ring buffer
and its meta-data structures, so that it's easier to understand
how changing the log buffer size (either through the command line or
by changing CONFIG_LOG_BUF_SHIFT) affects boot time memory usage.
With the new logs, it is much easier to see exactly why the memory
increased by 2304 KB:
log_buf_len=512K:
printk: log buffer data + meta data: 524288 + 1835008 = 2359296 bytes
Memory: ... (... 733252K reserved ...)
log_buf_len=1M:
printk: log buffer data + meta data: 1048576 + 3670016 = 4718592 bytes
Memory: ... (... 735556K reserved ...)
Signed-off-by: Isaac J. Manjarres <isaacmanjarres@google.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240930184826.3595221-1-isaacmanjarres@google.com
[pmladek@suse.com: Updated the examples in the commit message, simplified comment for default buffer.]
Signed-off-by: Petr Mladek <pmladek@suse.com>
Pull drm updates from Dave Airlie:
"This adds a couple of patches outside the drm core, all should be
acked appropriately, the string and pstore ones are the main ones that
come to mind.
Otherwise it's the usual drivers, xe is getting enabled by default on
some new hardware, we've changed the device number handling to allow
more devices, and we added some optional rust code to create QR codes
in the panic handler, an idea first suggested I think 10 years ago :-)
string:
- add mem_is_zero()
core:
- support more device numbers
- use XArray for minor ids
- add backlight constants
- Split dma fence array creation into alloc and arm
fbdev:
- remove usage of old fbdev hooks
kms:
- Add might_fault() to drm_modeset_lock priming
- Add dynamic per-crtc vblank configuration support
dma-buf:
- docs cleanup
buddy:
- Add start address support for trim function
printk:
- pass description to kmsg_dump
scheduler:
- Remove full_recover from drm_sched_start
ttm:
- Make LRU walk restartable after dropping locks
- Allow direct reclaim to allocate local memory
panic:
- add display QR code (in rust)
displayport:
- mst: GUID improvements
bridge:
- Silence error message on -EPROBE_DEFER
- analogix: Clean aup
- bridge-connector: Fix double free
- lt6505: Disable interrupt when powered off
- tc358767: Make default DP port preemphasis configurable
- lt9611uxc: require DRM_BRIDGE_ATTACH_NO_CONNECTOR
- anx7625: simplify OF array handling
- dw-hdmi: simplify clock handling
- lontium-lt8912b: fix mode validation
- nwl-dsi: fix mode vsync/hsync polarity
xe:
- Enable LunarLake and Battlemage support
- Introducing Xe2 ccs modifiers for integrated and discrete graphics
- rename xe perf to xe observation
- use wb caching on DGFX for system memory
- add fence timeouts
- Lunar Lake graphics/media/display workarounds
- Battlemage workarounds
- Battlemage GSC support
- GSC and HuC fw updates for LL/BM
- use dma_fence_chain_free
- refactor hw engine lookup and mmio access
- enable priority mem read for Xe2
- Add first GuC BMG fw
- fix dma-resv lock
- Fix DGFX display suspend/resume
- Use xe_managed for kernel BOs
- Use reserved copy engine for user binds on faulting devices
- Allow mixing dma-fence jobs and long-running faulting jobs
- fix media TLB invalidation
- fix rpm in TTM swapout path
- track resources and VF state by PF
i915:
- Type-C programming fix for MTL+
- FBC cleanup
- Calc vblank delay more accurately
- On DP MST, Enable LT fallback for UHBR<->non-UHBR rates
- Fix DP LTTPR detection
- limit relocations to INT_MAX
- fix long hangs in buddy allocator on DG2/A380
amdgpu:
- Per-queue reset support
- SDMA devcoredump support
- DCN 4.0.1 updates
- GFX12/VCN4/JPEG4 updates
- Convert vbios embedded EDID to drm_edid
- GFX9.3/9.4 devcoredump support
- process isolation framework for GFX 9.4.3/4
- take IOMMU mappings into account for P2P DMA
amdkfd:
- CRIU fixes
- HMM fix
- Enable process isolation support for GFX 9.4.3/4
- Allow users to target recommended SDMA engines
- KFD support for targetting queues on recommended SDMA engines
radeon:
- remove .load and drm_dev_alloc
- Fix vbios embedded EDID size handling
- Convert vbios embedded EDID to drm_edid
- Use GEM references instead of TTM
- r100 cp init cleanup
- Fix potential overflows in evergreen CS offset tracking
msm:
- DPU:
- implement DP/PHY mapping on SC8180X
- Enable writeback on SM8150, SC8180X, SM6125, SM6350
- DP:
- Enable widebus on all relevant chipsets
- MSM8998 HDMI support
- GPU:
- A642L speedbin support
- A615/A306/A621 support
- A7xx devcoredump support
ast:
- astdp: Support AST2600 with VGA
- Clean up HPD
- Fix timeout loop for DP link training
- reorganize output code by type (VGA, DP, etc)
- convert to struct drm_edid
- fix BMC handling for all outputs
exynos:
- drop stale MAINTAINERS pattern
- constify struct
loongson:
- use GEM refcount over TTM
mgag200:
- Improve BMC handling
- Support VBLANK intterupts
- transparently support BMC outputs
nouveau:
- Refactor and clean up internals
- Use GEM refcount over TTM's
gm12u320:
- convert to struct drm_edid
gma500:
- update i2c terms
lcdif:
- pixel clock fix
host1x:
- fix syncpoint IRQ during resume
- use iommu_paging_domain_alloc()
imx:
- ipuv3: convert to struct drm_edid
omapdrm:
- improve error handling
- use common helper for_each_endpoint_of_node()
panel:
- add support for BOE TV101WUM-LL2 plus DT bindings
- novatek-nt35950: improve error handling
- nv3051d: improve error handling
- panel-edp:
- add support for BOE NE140WUM-N6G
- revert support for SDC ATNA45AF01
- visionox-vtdr6130:
- improve error handling
- use devm_regulator_bulk_get_const()
- boe-th101mb31ig002:
- Support for starry-er88577 MIPI-DSI panel plus DT
- Fix porch parameter
- edp: Support AOU B116XTN02.3, AUO B116XAN06.1, AOU B116XAT04.1, BOE
NV140WUM-N41, BOE NV133WUM-N63, BOE NV116WHM-A4D, CMN N116BCA-EA2,
CMN N116BCP-EA2, CSW MNB601LS1-4
- himax-hx8394: Support Microchip AC40T08A MIPI Display panel plus DT
- ilitek-ili9806e: Support Densitron DMT028VGHMCMI-1D TFT plus DT
- jd9365da:
- Support Melfas lmfbx101117480 MIPI-DSI panel plus DT
- Refactor for code sharing
- panel-edp: fix name for HKC MB116AN01
- jd9365da: fix "exit sleep" commands
- jdi-fhd-r63452: simplify error handling with DSI multi-style
helpers
- mantix-mlaf057we51: simplify error handling with DSI multi-style
helpers
- simple:
- support Innolux G070ACE-LH3 plus DT bindings
- support On Tat Industrial Company KD50G21-40NT-A1 plus DT
bindings
- st7701:
- decouple DSI and DRM code
- add SPI support
- support Anbernic RG28XX plus DT bindings
mediatek:
- support alpha blending
- remove cl in struct cmdq_pkt
- ovl adaptor fix
- add power domain binding for mediatek DPI controller
renesas:
- rz-du: add support for RZ/G2UL plus DT bindings
rockchip:
- Improve DP sink-capability reporting
- dw_hdmi: Support 4k@60Hz
- vop:
- Support RGB display on Rockchip RK3066
- Support 4096px width
sti:
- convert to struct drm_edid
stm:
- Avoid UAF wih managed plane and CRTC helpers
- Fix module owner
- Fix error handling in probe
- Depend on COMMON_CLK
- ltdc:
- Fix transparency after disabling plane
- Remove unused interrupt
tegra:
- gr3d: improve PM domain handling
- convert to struct drm_edid
- Call drm_atomic_helper_shutdown()
vc4:
- fix PM during detect
- replace DRM_ERROR() with drm_error()
- v3d: simplify clock retrieval
v3d:
- Clean up perfmon
virtio:
- add DRM capset"
* tag 'drm-next-2024-09-19' of https://gitlab.freedesktop.org/drm/kernel: (1326 commits)
drm/xe: Fix missing conversion to xe_display_pm_runtime_resume
drm/xe/xe2hpg: Add Wa_15016589081
drm/xe: Don't keep stale pointer to bo->ggtt_node
drm/xe: fix missing 'xe_vm_put'
drm/xe: fix build warning with CONFIG_PM=n
drm/xe: Suppress missing outer rpm protection warning
drm/xe: prevent potential UAF in pf_provision_vf_ggtt()
drm/amd/display: Add all planes on CRTC to state for overlay cursor
drm/i915/bios: fix printk format width
drm/i915/display: Fix BMG CCS modifiers
drm/amdgpu: get rid of bogus includes of fdtable.h
drm/amdkfd: CRIU fixes
drm/amdgpu: fix a race in kfd_mem_export_dmabuf()
drm: new helper: drm_gem_prime_handle_to_dmabuf()
drm/amdgpu/atomfirmware: Silence UBSAN warning
drm/amdgpu: Fix kdoc entry in 'amdgpu_vm_cpu_prepare'
drm/amd/amdgpu: apply command submission parser for JPEG v1
drm/amd/amdgpu: apply command submission parser for JPEG v2+
drm/amd/pm: fix the pp_dpm_pcie issue on smu v14.0.2/3
drm/amd/pm: update the features set on smu v14.0.2/3
...
Pull printk updates from Petr Mladek:
"This is the "last" part of the support for the new nbcon consoles.
Where "nbcon" stays for "No Big console lock CONsoles" aka not under
the console_lock.
New callbacks are added to struct console:
- write_thread() for flushing nbcon consoles in task context.
- write_atomic() for flushing nbcon consoles in atomic context,
including NMI.
- con->device_lock() and device_unlock() for taking the driver
specific lock, for example, port->lock.
New printk-specific kthreads are created:
- per-console kthreads which get responsible for flushing normal
priority messages on nbcon consoles.
- thread which gets responsible for flushing normal priority messages
on all consoles when CONFIG_RT enabled.
The new callbacks are called under a special per-console lock which
has already been added back in v6.7. It allows to distinguish three
severities: normal, emergency, and panic. A context with a higher
priority could take over the ownership when it is safe even in the
middle of handling a record. The panic context could do it even when
it is not safe. But it is allowed only for the final desperate flush
before entering the infinite loop.
The new lock helps to flush the messages directly in emergency and
panic contexts. But it is not enough in all situations:
- console_lock() is still need for synchronization against boot
consoles.
- con->device_lock() is need for synchronization against other
operations on the same HW, e.g. serial port speed setting,
non-printk related read/write.
The dependency on con->device_lock() is mutual. Any code taking the
driver specific lock has to acquire the related nbcon console context
as well. For example, see the new uart_port_lock() API. It provides
the necessary synchronization against emergency and panic contexts
where the messages are flushed only under the new per-console lock.
Maybe surprisingly, a quite tricky part is the decision how to flush
the consoles in various situations. It has to take into account:
- message priority: normal, emergency, panic
- scheduling context: task, atomic, deferred_legacy
- registered consoles: boot, legacy, nbcon
- threads are running: early boot, suspend, shutdown, panic
- caller: printk(), pr_flush(), printk_flush_in_panic(),
console_unlock(), console_start(), ...
The primary decision is made in printk_get_console_flush_type(). It
creates a hint what the caller should do:
- flush nbcon consoles directly or via the kthread
- call the legacy loop (console_unlock()) directly or via irq_work
The existing behavior is preserved for the legacy consoles. The only
exception is that they are not longer flushed directly from printk()
in panic() before CPUs are stopped. But this blocking happens only
when at least one nbcon console is registered. The motivation is to
increase a chance to produce the crash dump. They legacy consoles
might create a deadlock in compare with nbcon consoles. The nbcon
console should allow to see the messages even when the crash dump
fails.
There are three possible ways how nbcon consoles are flushed:
- The per-nbcon-console kthread is responsible for flushing messages
added with the normal priority. This is the default mode.
- The legacy loop, aka console_unlock(), is used when there is still
a boot console registered. There is no easy way how to match an
early console driver with a nbcon console driver. And the
console_lock() provides the only reliable serialization at the
moment.
The legacy loop uses either con->write_atomic() or
con->write_thread() callbacks depending on whether it is allowed to
schedule. The atomic variant has to be used from printk().
- In other situations, the messages are flushed directly using
write_atomic() which can be called in any context, including NMI.
It is primary needed during early boot or shutdown, in emergency
situations, and panic.
The emergency priority is used by a code called within
nbcon_cpu_emergency_enter()/exit(). At the moment, it is used in four
situations: WARN(), Oops, lockdep, and RCU stall reports.
Finally, there is no nbcon console at the moment. It means that the
changes should _not_ modify the existing behavior. The only exception
is CONFIG_RT which would force offloading the legacy loop, for normal
priority context, into the dedicated kthread"
* tag 'printk-for-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: (54 commits)
printk: Avoid false positive lockdep report for legacy printing
printk: nbcon: Assign nice -20 for printing threads
printk: Implement legacy printer kthread for PREEMPT_RT
tty: sysfs: Add nbcon support for 'active'
proc: Add nbcon support for /proc/consoles
proc: consoles: Add notation to c_start/c_stop
printk: nbcon: Show replay message on takeover
printk: Provide helper for message prepending
printk: nbcon: Rely on kthreads for normal operation
printk: nbcon: Use thread callback if in task context for legacy
printk: nbcon: Relocate nbcon_atomic_emit_one()
printk: nbcon: Introduce printer kthreads
printk: nbcon: Init @nbcon_seq to highest possible
printk: nbcon: Add context to usable() and emit()
printk: Flush console on unregister_console()
printk: Fail pr_flush() if before SYSTEM_SCHEDULING
printk: nbcon: Add function for printers to reacquire ownership
printk: nbcon: Use raw_cpu_ptr() instead of open coding
printk: Use the BITS_PER_LONG macro
lockdep: Mark emergency sections in lockdep splats
...
Legacy console printing from printk() caller context may invoke
the console driver from atomic context. This leads to a lockdep
splat because the console driver will acquire a sleeping lock
and the caller may already hold a spinning lock. This is noticed
by lockdep on !PREEMPT_RT configurations because it will lead to
a problem on PREEMPT_RT.
However, on PREEMPT_RT the printing path from atomic context is
always avoided and the console driver is always invoked from a
dedicated thread. Thus the lockdep splat on !PREEMPT_RT is a
false positive.
For !PREEMPT_RT override the lock-context before invoking the
console driver to avoid the false positive.
Do not override the lock-context for PREEMPT_RT in order to
allow lockdep to catch any real locking context issues related
to the write callback usage.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240904120536.115780-18-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
The write() callback of legacy consoles usually makes use of
spinlocks. This is not permitted with PREEMPT_RT in atomic
contexts.
For PREEMPT_RT, create a new kthread to handle printing of all
the legacy consoles (and nbcon consoles if boot consoles are
registered). This allows legacy consoles to work on PREEMPT_RT
without requiring modification. (However they will not have
the reliability properties guaranteed by nbcon atomic
consoles.)
Use the existing printk_kthreads_check_locked() to start/stop
the legacy kthread as needed.
Introduce the macro force_legacy_kthread() to query if the
forced threading of legacy consoles is in effect. Although
currently only enabled for PREEMPT_RT, this acts as a simple
mechanism for the future to allow other preemption models to
easily take advantage of the non-interference property provided
by the legacy kthread.
When force_legacy_kthread() is true, the legacy kthread
fulfills the role of the console_flush_type @legacy_offload by
waking the legacy kthread instead of printing via the
console_lock in the irq_work. If the legacy kthread is not
yet available, no legacy printing takes place (unless in
panic).
If for some reason the legacy kthread fails to create, any
legacy consoles are unregistered. With force_legacy_kthread(),
the legacy kthread is a critical component for legacy consoles.
These changes only affect CONFIG_PREEMPT_RT.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240904120536.115780-16-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
An emergency or panic context can takeover console ownership
while the current owner was printing a printk message. The
atomic printer will re-print the message that the previous
owner was printing. However, this can look confusing to the
user and may even seem as though a message was lost.
[3430014.1
[3430014.181123] usb 1-2: Product: USB Audio
Add a new field @nbcon_prev_seq to struct console to track
the sequence number to print that was assigned to the previous
console owner. If this matches the sequence number to print
that the current owner is assigned, then a takeover must have
occurred. In this case, print an additional message to inform
the user that the previous message is being printed again.
[3430014.1
** replaying previous printk message **
[3430014.181123] usb 1-2: Product: USB Audio
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240904120536.115780-12-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
