Commit 9a0f53e0 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'csd-lock.2023.10.23a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu 

Pull CSD lock update from Paul McKenney:
 "This adds a kernel boot parameter that causes the kernel to panic if
  one of the call_smp_function() APIs is stalled for more than the
  specified duration.

  This is useful in deployments in which a clean panic is preferable to
  an indefinite stall"

* tag 'csd-lock.2023.10.23a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  smp,csd: Throw an error if a CSD lock is stuck for too long
parents 6750f0de 94b3f0b5

Documentation/admin-guide/kernel-parameters.txt

+7 −0
Original line number Diff line number Diff line
@@ -5864,6 +5864,13 @@ 
			This feature may be more efficiently disabled

			using the csdlock_debug- kernel parameter.



	smp.panic_on_ipistall= [KNL]

			If a csd_lock_timeout extends for more than

			the specified number of milliseconds, panic the

			system.  By default, let CSD-lock acquisition

			take as long as they take.  Specifying 300,000

			for this value provides a 5-minute timeout.



	smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices

	smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port

	smsc-ircc2.ircc_sir=	[HW] SIR base I/O port

kernel/smp.c

+12 −1
Original line number Diff line number Diff line
@@ -170,6 +170,8 @@ static DEFINE_PER_CPU(void *, cur_csd_info); 


static ulong csd_lock_timeout = 5000;  /* CSD lock timeout in milliseconds. */

module_param(csd_lock_timeout, ulong, 0444);

static int panic_on_ipistall;  /* CSD panic timeout in milliseconds, 300000 for five minutes. */

module_param(panic_on_ipistall, int, 0444);



static atomic_t csd_bug_count = ATOMIC_INIT(0);
@@ -230,6 +232,7 @@ static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, in 
	}



	ts2 = sched_clock();

	/* How long since we last checked for a stuck CSD lock.*/

	ts_delta = ts2 - *ts1;

	if (likely(ts_delta <= csd_lock_timeout_ns || csd_lock_timeout_ns == 0))

		return false;
@@ -243,9 +246,17 @@ static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, in 
	else

		cpux = cpu;

	cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */

	/* How long since this CSD lock was stuck. */

	ts_delta = ts2 - ts0;

	pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %llu ns for CPU#%02d %pS(%ps).\n",

		 firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), ts2 - ts0,

		 firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), ts_delta,

		 cpu, csd->func, csd->info);

	/*

	 * If the CSD lock is still stuck after 5 minutes, it is unlikely

	 * to become unstuck. Use a signed comparison to avoid triggering

	 * on underflows when the TSC is out of sync between sockets.

	 */

	BUG_ON(panic_on_ipistall > 0 && (s64)ts_delta > ((s64)panic_on_ipistall * NSEC_PER_MSEC));

	if (cpu_cur_csd && csd != cpu_cur_csd) {

		pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n",

			 *bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)),