6.12-stable review patch. If anyone has any objections, please let me know.
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From: Fernando Fernandez Mancera ffmancera@riseup.net
[ Upstream commit 3940f5349b476197fb079c5aa19c9a988de64efb ]
There's a lockdep false positive warning related to i8253_lock:
WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected ... systemd-sleep/3324 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: ffffffffb2c23398 (i8253_lock){+.+.}-{2:2}, at: pcspkr_event+0x3f/0xe0 [pcspkr]
... ... which became HARDIRQ-irq-unsafe at: ... lock_acquire+0xd0/0x2f0 _raw_spin_lock+0x30/0x40 clockevent_i8253_disable+0x1c/0x60 pit_timer_init+0x25/0x50 hpet_time_init+0x46/0x50 x86_late_time_init+0x1b/0x40 start_kernel+0x962/0xa00 x86_64_start_reservations+0x24/0x30 x86_64_start_kernel+0xed/0xf0 common_startup_64+0x13e/0x141 ...
Lockdep complains due pit_timer_init() using the lock in an IRQ-unsafe fashion, but it's a false positive, because there is no deadlock possible at that point due to init ordering: at the point where pit_timer_init() is called there is no other possible usage of i8253_lock because the system is still in the very early boot stage with no interrupts.
But in any case, pit_timer_init() should disable interrupts before calling clockevent_i8253_disable() out of general principle, and to keep lockdep working even in this scenario.
Use scoped_guard() for that, as suggested by Thomas Gleixner.
[ mingo: Cleaned up the changelog. ]
Suggested-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Fernando Fernandez Mancera ffmancera@riseup.net Signed-off-by: Ingo Molnar mingo@kernel.org Reviewed-by: Thomas Gleixner tglx@linutronix.de Link: https://lore.kernel.org/r/Z-uwd4Bnn7FcCShX@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/i8253.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/i8253.c b/arch/x86/kernel/i8253.c index 80e262bb627fe..cb9852ad60989 100644 --- a/arch/x86/kernel/i8253.c +++ b/arch/x86/kernel/i8253.c @@ -46,7 +46,8 @@ bool __init pit_timer_init(void) * VMMs otherwise steal CPU time just to pointlessly waggle * the (masked) IRQ. */ - clockevent_i8253_disable(); + scoped_guard(irq) + clockevent_i8253_disable(); return false; } clockevent_i8253_init(true);