Merge branch 'rework/fixes' into for-linus (3db488c8) · Commits · git / linux-net

kernel/printk/nbcon.c

+41 −22

Original line number	Diff line number	Diff line
		@@ -216,6 +216,7 @@ static void nbcon_seq_try_update(struct nbcon_context *ctxt, u64 new_seq)
		* nbcon_context_try_acquire_direct - Try to acquire directly
		* @ctxt: The context of the caller
		* @cur: The current console state
		* @is_reacquire: This acquire is a reacquire
		*
		* Acquire the console when it is released. Also acquire the console when
		* the current owner has a lower priority and the console is in a safe state.
		@@ -225,17 +226,17 @@ static void nbcon_seq_try_update(struct nbcon_context *ctxt, u64 new_seq)
		*
		* Errors:
		*
		* -EPERM: A panic is in progress and this is not the panic CPU.
		* Or the current owner or waiter has the same or higher
		* priority. No acquire method can be successful in
		* this case.
		* -EPERM: A panic is in progress and this is neither the panic
		* CPU nor is this a reacquire. Or the current owner or
		* waiter has the same or higher priority. No acquire
		* method can be successful in these cases.
		*
		* -EBUSY: The current owner has a lower priority but the console
		* in an unsafe state. The caller should try using
		* the handover acquire method.
		*/
		static int nbcon_context_try_acquire_direct(struct nbcon_context *ctxt,
		struct nbcon_state *cur)
		struct nbcon_state *cur, bool is_reacquire)
		{
		unsigned int cpu = smp_processor_id();
		struct console *con = ctxt->console;
		@@ -243,14 +244,20 @@ static int nbcon_context_try_acquire_direct(struct nbcon_context *ctxt,

		do {
		/*
		* Panic does not imply that the console is owned. However, it
		* is critical that non-panic CPUs during panic are unable to
		* acquire ownership in order to satisfy the assumptions of
		* nbcon_waiter_matches(). In particular, the assumption that
		* lower priorities are ignored during panic.
		*/
		if (other_cpu_in_panic())
		* Panic does not imply that the console is owned. However,
		* since all non-panic CPUs are stopped during panic(), it
		* is safer to have them avoid gaining console ownership.
		*
		* If this acquire is a reacquire (and an unsafe takeover
		* has not previously occurred) then it is allowed to attempt
		* a direct acquire in panic. This gives console drivers an
		* opportunity to perform any necessary cleanup if they were
		* interrupted by the panic CPU while printing.
		*/
		if (other_cpu_in_panic() &&
		(!is_reacquire \|\| cur->unsafe_takeover)) {
		return -EPERM;
		}

		if (ctxt->prio <= cur->prio \|\| ctxt->prio <= cur->req_prio)
		return -EPERM;
		@@ -301,8 +308,9 @@ static bool nbcon_waiter_matches(struct nbcon_state *cur, int expected_prio)
		* Event #1 implies this context is EMERGENCY.
		* Event #2 implies the new context is PANIC.
		* Event #3 occurs when panic() has flushed the console.
		* Events #4 and #5 are not possible due to the other_cpu_in_panic()
		* check in nbcon_context_try_acquire_direct().
		* Event #4 occurs when a non-panic CPU reacquires.
		* Event #5 is not possible due to the other_cpu_in_panic() check
		* in nbcon_context_try_acquire_handover().
		*/

		return (cur->req_prio == expected_prio);
		@@ -431,6 +439,16 @@ static int nbcon_context_try_acquire_handover(struct nbcon_context *ctxt,
		WARN_ON_ONCE(ctxt->prio <= cur->prio \|\| ctxt->prio <= cur->req_prio);
		WARN_ON_ONCE(!cur->unsafe);

		/*
		* Panic does not imply that the console is owned. However, it
		* is critical that non-panic CPUs during panic are unable to
		* wait for a handover in order to satisfy the assumptions of
		* nbcon_waiter_matches(). In particular, the assumption that
		* lower priorities are ignored during panic.
		*/
		if (other_cpu_in_panic())
		return -EPERM;

		/* Handover is not possible on the same CPU. */
		if (cur->cpu == cpu)
		return -EBUSY;
		@@ -559,6 +577,7 @@ static struct printk_buffers panic_nbcon_pbufs;
		/**
		* nbcon_context_try_acquire - Try to acquire nbcon console
		* @ctxt: The context of the caller
		* @is_reacquire: This acquire is a reacquire
		*
		* Context: Under @ctxt->con->device_lock() or local_irq_save().
		* Return: True if the console was acquired. False otherwise.
		@@ -568,7 +587,7 @@ static struct printk_buffers panic_nbcon_pbufs;
		* in an unsafe state. Otherwise, on success the caller may assume
		* the console is not in an unsafe state.
		*/
		static bool nbcon_context_try_acquire(struct nbcon_context *ctxt)
		static bool nbcon_context_try_acquire(struct nbcon_context *ctxt, bool is_reacquire)
		{
		unsigned int cpu = smp_processor_id();
		struct console *con = ctxt->console;
		@@ -577,7 +596,7 @@ static bool nbcon_context_try_acquire(struct nbcon_context *ctxt)

		nbcon_state_read(con, &cur);
		try_again:
		err = nbcon_context_try_acquire_direct(ctxt, &cur);
		err = nbcon_context_try_acquire_direct(ctxt, &cur, is_reacquire);
		if (err != -EBUSY)
		goto out;

		@@ -913,7 +932,7 @@ void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt)
		{
		struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);

		while (!nbcon_context_try_acquire(ctxt))
		while (!nbcon_context_try_acquire(ctxt, true))
		cpu_relax();

		nbcon_write_context_set_buf(wctxt, NULL, 0);
		@@ -1101,7 +1120,7 @@ static bool nbcon_emit_one(struct nbcon_write_context *wctxt, bool use_atomic)
		cant_migrate();
		}

		if (!nbcon_context_try_acquire(ctxt))
		if (!nbcon_context_try_acquire(ctxt, false))
		goto out;

		/*
		@@ -1486,7 +1505,7 @@ static int __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq,
		ctxt->prio = nbcon_get_default_prio();
		ctxt->allow_unsafe_takeover = allow_unsafe_takeover;

		if (!nbcon_context_try_acquire(ctxt))
		if (!nbcon_context_try_acquire(ctxt, false))
		return -EPERM;

		while (nbcon_seq_read(con) < stop_seq) {
		@@ -1784,7 +1803,7 @@ bool nbcon_device_try_acquire(struct console *con)
		ctxt->console = con;
		ctxt->prio = NBCON_PRIO_NORMAL;

		if (!nbcon_context_try_acquire(ctxt))
		if (!nbcon_context_try_acquire(ctxt, false))
		return false;

		if (!nbcon_context_enter_unsafe(ctxt))