CC+ printk folks On Thu, Dec 12 2024 at 11:07, David Woodhouse wrote: > On Wed, 2024-12-11 at 07:42 -0500, Stefan Hajnoczi wrote: >> On Tue, Dec 10, 2024 at 09:56:43AM +0800, Jason Wang wrote: >> > Adding more virtio-blk people here. >> >> Please try Ming Lei's recent fix in Jens' tree: >> >> virtio-blk: don't keep queue frozen during system suspend >> commit: 7678abee0867e6b7fb89aa40f6e9f575f755fb37 >> >> https://git.kernel.dk/cgit/linux/commit/?h=block-6.13&id=7678abee0867e6b7fb89aa40f6e9f575f755fb37 > > Thanks. That does make those warnings go away. I do still get this one > occasionally though. It seems to go away without 'no_console_suspend' > on the command line, but I'm not sure that makes it OK. Not really. > [ 23.665790] Interrupts enabled after irqrouter_resume+0x0/0x50 The resume callback irqrouter_resume() returns with interrupts enabled, but it's absolutely unclear where this happens. The lockdep tracking is not really helpful: > [ 23.697043] hardirqs last enabled at (15573): [<ffffffffa8281b8e>] __up_console_sem+0x7e/0x90 > [ 23.697855] hardirqs last disabled at (15580): [<ffffffffa8281b73>] __up_console_sem+0x63/0x90 __up_console_sem() { printk_safe_enter_irqsave(flags); // Assuming this is __up_console_sem+0x63/0x90 // Saves state in @flags and disables interrupts up(&console_sem); printk_safe_exit_irqrestore(flags); // Assuming this is __up_console_sem+0x7e/0x90 // Restores the interrupt state from @flags } Though the events are in reverse order: last enabled at 15573 last disabled at 15580 At event #15573 printk_safe_exit_irqrestore(flags) enabled interrupts, which means the preceeding printk_safe_enter_irqsave(flags) was invoked with interrupts enabled. But that enable event wiped the real culprit, which enabled interrupts before __up_console_sem() was invoked. At event #15580 printk_safe_enter_irqsave(flags); disables interrupts again, which is probably at the point where printk() dumps the bug, but I might be misreading this. Now David's observation that the problem "goes away" when he adds "no_console_suspend" on the command line is definitely interesting, but does not really help in figuring out the root cause. > [ 23.698673] softirqs last enabled at (14798): [<ffffffffa81c6c12>] __irq_exit_rcu+0xe2/0x100 > [ 23.699481] softirqs last disabled at (14777): [<ffffffffa81c6c12>] __irq_exit_rcu+0xe2/0x100 > [ 23.700284] ---[ end trace 0000000000000000 ]--- > [ 23.702460] ------------[ cut here ]------------ > [ 23.702963] WARNING: CPU: 0 PID: 560 at kernel/time/hrtimer.c:995 hrtimers_resume_local+0x29/0x40 This one is just a consequence of the above. David, can you retest with the debug patch below? That should pin-point the real culprit. Thanks, tglx --- --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -621,6 +621,9 @@ do { \ extern void lockdep_assert_in_softirq_func(void); +extern void lockdep_suspend_syscore_enter(void); +extern void lockdep_suspend_syscore_exit(void); + #else # define might_lock(lock) do { } while (0) # define might_lock_read(lock) do { } while (0) @@ -635,6 +638,8 @@ extern void lockdep_assert_in_softirq_fu # define lockdep_assert_preemption_disabled() do { } while (0) # define lockdep_assert_in_softirq() do { } while (0) # define lockdep_assert_in_softirq_func() do { } while (0) +static inline void lockdep_suspend_syscore_enter(void) { } +static inline void lockdep_suspend_syscore_exit(void) { } #endif #ifdef CONFIG_PROVE_RAW_LOCK_NESTING --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -1025,6 +1025,7 @@ int kernel_kexec(void) if (error) goto Enable_cpus; local_irq_disable(); + lockdep_suspend_syscore_enter(); error = syscore_suspend(); if (error) goto Enable_irqs; @@ -1054,6 +1055,7 @@ int kernel_kexec(void) if (kexec_image->preserve_context) { syscore_resume(); Enable_irqs: + lockdep_suspend_syscore_exit(); local_irq_enable(); Enable_cpus: suspend_enable_secondary_cpus(); --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -4408,6 +4408,18 @@ void lockdep_hardirqs_on_prepare(void) } EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare); +static bool suspend_syscore_active; + +void noinstr lockdep_suspend_syscore_enter(void) +{ + suspend_syscore_active = true; +} + +void noinstr lockdep_suspend_syscore_exit(void) +{ + suspend_syscore_active = false; +} + void noinstr lockdep_hardirqs_on(unsigned long ip) { struct irqtrace_events *trace = ¤t->irqtrace; @@ -4456,6 +4468,8 @@ void noinstr lockdep_hardirqs_on(unsigne if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return; + DEBUG_LOCKS_WARN_ON(suspend_syscore_active); + /* * Ensure the lock stack remained unchanged between * lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on().
