Alexey reports lockdep_assert_irqs_enabled() warnings when stress testing perf,
e.g.,
WARNING: CPU: 0 PID: 1556 at kernel/softirq.c:169
__local_bh_enable_ip+0x258/0x270
CPU: 0 PID: 1556 Comm: syz-executor
NIP: c0000000001ec888 LR: c0000000001ec884 CTR: c000000000ef0610
REGS: c000000022d4f8a0 TRAP: 0700 Not tainted (5.8.0-rc3-x)
MSR: 8000000000029033 <SF,EE,ME,IR,DR,RI,LE> CR: 28008844 XER: 20040000
CFAR: c0000000001dc1d0 IRQMASK: 0
The interesting thing is MSR[EE] and IRQMASK shows interrupts are enabled,
suggesting the current->hardirqs_enabled irq tracing state is going out of sync
with the actual interrupt enable state.
The cause is a window in interrupt/syscall return where irq tracing state is
being
adjusted for an irqs-enabled return while MSR[EE] is still enabled. A perf
interrupt hits and ends up calling trace_hardirqs_off() when restoring
interrupt flags to a disable state.
Fix this by disabling perf interrupts as well while adjusting irq tracing state.
Add a debug check that catches the condition sooner.
Fixes: 68b34588e202 ("powerpc/64/sycall: Implement syscall entry/exit logic in
C")
Reported-by: Alexey Kardashevskiy <a...@ozlabs.ru>
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
I can reproduce similar symptoms and this patch fixes my test case,
still trying to confirm Alexey's test case or whether there's another
similar bug causing it.
arch/powerpc/kernel/syscall_64.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c
index 79edba3ab312..6c6f88eff915 100644
--- a/arch/powerpc/kernel/syscall_64.c
+++ b/arch/powerpc/kernel/syscall_64.c
@@ -107,8 +107,13 @@ notrace long system_call_exception(long r3, long r4, long
r5,
*/
static notrace inline bool prep_irq_for_enabled_exit(void)
{
- /* This must be done with RI=1 because tracing may touch vmaps */
- trace_hardirqs_on();
+ if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS)) {
+ /* Prevent perf interrupts hitting and messing up the
trace_hardirqs state */
+ irq_soft_mask_set(IRQS_ALL_DISABLED);
+
+ /* This must be done with RI=1 because tracing may touch vmaps
*/
+ trace_hardirqs_on();
+ }
/* This pattern matches prep_irq_for_idle */
__hard_EE_RI_disable();
@@ -123,6 +128,8 @@ static notrace inline bool prep_irq_for_enabled_exit(void)
local_paca->irq_happened = 0;
irq_soft_mask_set(IRQS_ENABLED);
+ lockdep_assert_irqs_enabled();
+
return true;
}
--
2.23.0
