[PATCH] clocksource: disable irq when holding watchdog_lock.
From: Tetsuo Handa
Date: Fri Oct 13 2023 - 10:51:58 EST
Lockdep found that spin_lock(&watchdog_lock) from call_timer_fn()
is not safe. Use spin_lock_irqsave(&watchdog_lock, flags) instead.
[ 0.378387] TSC synchronization [CPU#0 -> CPU#1]:
[ 0.378387] Measured 55060 cycles TSC warp between CPUs, turning off TSC clock.
[ 0.378387] tsc: Marking TSC unstable due to check_tsc_sync_source failed
[ 0.926101]
[ 0.926387] ================================
[ 0.926387] WARNING: inconsistent lock state
[ 0.926387] 6.6.0-rc5-00192-g10a6e5feccb8 #2 Not tainted
[ 0.926387] --------------------------------
[ 0.926387] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
[ 0.926387] swapper/0/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
[ 0.926387] ffffffff8cfa1c78 (watchdog_lock){?.-.}-{2:2}, at: clocksource_watchdog+0x23/0x5a0
[ 0.926387] {IN-HARDIRQ-W} state was registered at:
[ 0.926387] lock_acquire+0xc1/0x2c0
[ 0.926387] _raw_spin_lock_irqsave+0x3f/0x60
[ 0.926387] clocksource_mark_unstable+0x1b/0x90
[ 0.926387] mark_tsc_unstable+0x41/0x50
[ 0.926387] check_tsc_sync_source+0x14f/0x180
[ 0.926387] __flush_smp_call_function_queue+0x16f/0x560
[ 0.926387] __sysvec_call_function_single+0x36/0x110
[ 0.926387] sysvec_call_function_single+0x69/0x90
[ 0.926387] asm_sysvec_call_function_single+0x1a/0x20
[ 0.926387] default_idle+0xf/0x20
[ 0.926387] default_idle_call+0x7f/0x180
[ 0.926387] do_idle+0x1e1/0x220
[ 0.926387] cpu_startup_entry+0x2a/0x30
[ 0.926387] rest_init+0xf4/0x190
[ 0.926387] arch_call_rest_init+0xe/0x30
[ 0.926387] start_kernel+0x763/0x910
[ 0.926387] x86_64_start_reservations+0x18/0x30
[ 0.926387] x86_64_start_kernel+0xca/0xe0
[ 0.926387] secondary_startup_64_no_verify+0x178/0x17b
[ 0.926387] irq event stamp: 138774
[ 0.926387] hardirqs last enabled at (138774): [<ffffffff8bb99968>] _raw_spin_unlock_irq+0x28/0x50
[ 0.926387] hardirqs last disabled at (138773): [<ffffffff8bb99687>] _raw_spin_lock_irq+0x47/0x50
[ 0.926387] softirqs last enabled at (138216): [<ffffffff8b0904ff>] irq_exit_rcu+0x7f/0xa0
[ 0.926387] softirqs last disabled at (138267): [<ffffffff8b0904ff>] irq_exit_rcu+0x7f/0xa0
[ 0.926387]
[ 0.926387] other info that might help us debug this:
[ 0.926387] Possible unsafe locking scenario:
[ 0.926387]
[ 0.926387] CPU0
[ 0.926387] ----
[ 0.926387] lock(watchdog_lock);
[ 0.926387] <Interrupt>
[ 0.926387] lock(watchdog_lock);
[ 0.926387]
[ 0.926387] *** DEADLOCK ***
[ 0.926387]
[ 0.926387] 1 lock held by swapper/0/0:
[ 0.926387] #0: ffffa2d680003ea0 ((&watchdog_timer)){+.-.}-{0:0}, at: call_timer_fn+0x77/0x220
[ 0.926387]
[ 0.926387] stack backtrace:
[ 0.926387] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.6.0-rc5-00192-g10a6e5feccb8 #2
[ 0.926387] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
[ 0.926387] Call Trace:
[ 0.926387] <IRQ>
[ 0.926387] dump_stack_lvl+0x4b/0x80
[ 0.926387] mark_lock.part.0+0xa1c/0xf30
[ 0.926387] __lock_acquire+0x3a9/0x2550
[ 0.926387] lock_acquire+0xc1/0x2c0
[ 0.926387] ? clocksource_watchdog+0x23/0x5a0
[ 0.926387] ? __pfx_clocksource_watchdog+0x10/0x10
[ 0.926387] ? __pfx_clocksource_watchdog+0x10/0x10
[ 0.926387] _raw_spin_lock+0x30/0x40
[ 0.926387] ? clocksource_watchdog+0x23/0x5a0
[ 0.926387] clocksource_watchdog+0x23/0x5a0
[ 0.926387] ? __run_timers.part.0+0x30/0x2c0
[ 0.926387] ? __pfx_clocksource_watchdog+0x10/0x10
[ 0.926387] ? __pfx_clocksource_watchdog+0x10/0x10
[ 0.926387] call_timer_fn+0xa5/0x220
[ 0.926387] __run_timers.part.0+0x200/0x2c0
[ 0.926387] run_timer_softirq+0x2a/0x50
[ 0.926387] __do_softirq+0xc4/0x3c8
[ 0.926387] irq_exit_rcu+0x7f/0xa0
[ 0.926387] sysvec_apic_timer_interrupt+0x6e/0x90
[ 0.926387] </IRQ>
[ 0.926387] <TASK>
[ 0.926387] asm_sysvec_apic_timer_interrupt+0x1a/0x20
[ 0.926387] RIP: 0010:default_idle+0xf/0x20
[ 0.926387] Code: 4c 01 c7 4c 29 c2 e9 72 ff ff ff 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d 03 a9 27 00 fb f4 <fa> c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90
[ 0.926387] RSP: 0000:ffffffff8c803e70 EFLAGS: 00010206
[ 0.926387] RAX: 0000000000021bed RBX: ffffffff8c8369c0 RCX: 4000000000000000
[ 0.926387] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8b0f0091
[ 0.926387] RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001
[ 0.926387] R10: 0000000000000028 R11: 0000000000000000 R12: 0000000000000000
[ 0.926387] R13: 0000000000000000 R14: ffffffff8c836038 R15: 0000000000000095
[ 0.926387] ? do_idle+0x1e1/0x220
[ 0.926387] default_idle_call+0x7f/0x180
[ 0.926387] do_idle+0x1e1/0x220
[ 0.926387] cpu_startup_entry+0x2a/0x30
[ 0.926387] rest_init+0xf4/0x190
[ 0.926387] arch_call_rest_init+0xe/0x30
[ 0.926387] start_kernel+0x763/0x910
[ 0.926387] x86_64_start_reservations+0x18/0x30
[ 0.926387] x86_64_start_kernel+0xca/0xe0
[ 0.926387] secondary_startup_64_no_verify+0x178/0x17b
[ 0.926387] </TASK>
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
kernel/time/clocksource.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index c108ed8a9804..4e8fc0a5ca9d 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -405,8 +405,9 @@ static void clocksource_watchdog(struct timer_list *unused)
enum wd_read_status read_ret;
unsigned long extra_wait = 0;
u32 md;
+ unsigned long flags;
- spin_lock(&watchdog_lock);
+ spin_lock_irqsave(&watchdog_lock, flags);
if (!watchdog_running)
goto out;
@@ -554,7 +555,7 @@ static void clocksource_watchdog(struct timer_list *unused)
add_timer_on(&watchdog_timer, next_cpu);
}
out:
- spin_unlock(&watchdog_lock);
+ spin_unlock_irqrestore(&watchdog_lock, flags);
}
static inline void clocksource_start_watchdog(void)
--
2.34.1