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lockdep: Add lockdep_cleanup_dead_cpu()

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Add a function to check that an offline CPU has left the tracing
infrastructure in a sane state.

Commit 9bb69ba4c1 ("ACPI: processor_idle: use raw_safe_halt() in
acpi_idle_play_dead()") fixed an issue where the acpi_idle_play_dead()
function called safe_halt() instead of raw_safe_halt(), which had the
side-effect of setting the hardirqs_enabled flag for the offline CPU.

On x86 this triggered warnings from lockdep_assert_irqs_disabled() when
the CPU was brought back online again later. These warnings were too
early for the exception to be handled correctly, leading to a
triple-fault.

Add lockdep_cleanup_dead_cpu() to check for this kind of failure mode,
print the events leading up to it, and correct it so that the CPU can
come online again correctly. Re-introducing the original bug now merely
results in this warning instead:

[   61.556652] smpboot: CPU 1 is now offline
[   61.556769] CPU 1 left hardirqs enabled!
[   61.556915] irq event stamp: 128149
[   61.556965] hardirqs last  enabled at (128149): [<ffffffff81720a36>] acpi_idle_play_dead+0x46/0x70
[   61.557055] hardirqs last disabled at (128148): [<ffffffff81124d50>] do_idle+0x90/0xe0
[   61.557117] softirqs last  enabled at (128078): [<ffffffff81cec74c>] __do_softirq+0x31c/0x423
[   61.557199] softirqs last disabled at (128065): [<ffffffff810baae1>] __irq_exit_rcu+0x91/0x100

[boqun: Capitalize the title and reword the message a bit]

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/f7bd2b3b999051bb3ef4be34526a9262008285f5.camel@infradead.org
This commit is contained in:
David Woodhouse 2024-09-26 16:17:37 +01:00 committed by Boqun Feng
parent 87347f1480
commit 0784181b44
3 changed files with 31 additions and 0 deletions
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6
include/linux/irqflags.h
View File

@ -18,6 +18,8 @@
#include <asm/irqflags.h> #include <asm/irqflags.h>
#include <asm/percpu.h> #include <asm/percpu.h>
struct task_struct;
/* Currently lockdep_softirqs_on/off is used only by lockdep */ /* Currently lockdep_softirqs_on/off is used only by lockdep */
#ifdef CONFIG_PROVE_LOCKING #ifdef CONFIG_PROVE_LOCKING
extern void lockdep_softirqs_on(unsigned long ip); extern void lockdep_softirqs_on(unsigned long ip);
@ -25,12 +27,16 @@
extern void lockdep_hardirqs_on_prepare(void); extern void lockdep_hardirqs_on_prepare(void);
extern void lockdep_hardirqs_on(unsigned long ip); extern void lockdep_hardirqs_on(unsigned long ip);
extern void lockdep_hardirqs_off(unsigned long ip); extern void lockdep_hardirqs_off(unsigned long ip);
extern void lockdep_cleanup_dead_cpu(unsigned int cpu,
struct task_struct *idle);
#else #else
static inline void lockdep_softirqs_on(unsigned long ip) { } static inline void lockdep_softirqs_on(unsigned long ip) { }
static inline void lockdep_softirqs_off(unsigned long ip) { } static inline void lockdep_softirqs_off(unsigned long ip) { }
static inline void lockdep_hardirqs_on_prepare(void) { } static inline void lockdep_hardirqs_on_prepare(void) { }
static inline void lockdep_hardirqs_on(unsigned long ip) { } static inline void lockdep_hardirqs_on(unsigned long ip) { }
static inline void lockdep_hardirqs_off(unsigned long ip) { } static inline void lockdep_hardirqs_off(unsigned long ip) { }
static inline void lockdep_cleanup_dead_cpu(unsigned int cpu,
struct task_struct *idle) {}
#endif #endif
#ifdef CONFIG_TRACE_IRQFLAGS #ifdef CONFIG_TRACE_IRQFLAGS

1
kernel/cpu.c
View File

@ -1338,6 +1338,7 @@ static int takedown_cpu(unsigned int cpu)
cpuhp_bp_sync_dead(cpu); cpuhp_bp_sync_dead(cpu);
lockdep_cleanup_dead_cpu(cpu, idle_thread_get(cpu));
tick_cleanup_dead_cpu(cpu); tick_cleanup_dead_cpu(cpu);
/* /*

24
kernel/locking/lockdep.c
View File

@ -4586,6 +4586,30 @@ void lockdep_softirqs_off(unsigned long ip)
debug_atomic_inc(redundant_softirqs_off); debug_atomic_inc(redundant_softirqs_off);
} }
/**
* lockdep_cleanup_dead_cpu - Ensure CPU lockdep state is cleanly stopped
*
* @cpu: index of offlined CPU
* @idle: task pointer for offlined CPU's idle thread
*
* Invoked after the CPU is dead. Ensures that the tracing infrastructure
* is left in a suitable state for the CPU to be subsequently brought
* online again.
*/
void lockdep_cleanup_dead_cpu(unsigned int cpu, struct task_struct *idle)
{
if (unlikely(!debug_locks))
return;
if (unlikely(per_cpu(hardirqs_enabled, cpu))) {
pr_warn("CPU %u left hardirqs enabled!", cpu);
if (idle)
print_irqtrace_events(idle);
/* Clean it up for when the CPU comes online again. */
per_cpu(hardirqs_enabled, cpu) = 0;
}
}
static int static int
mark_usage(struct task_struct *curr, struct held_lock *hlock, int check) mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
{ {