Em Wed, Jul 26, 2023 at 08:10:45AM +0200, Mike Galbraith escreveu:
> On Tue, 2023-07-25 at 17:15 -0300, Arnaldo Carvalho de Melo wrote:
> > Hi Marco, Peter,
> > I got a report that 'perf test sigtrap' test failed on a
> > PREEMPT_RT_FULL kernel, one that had up to:
> > commit 97ba62b278674293762c3d91f724f1bb922f04e0
> > Author: Marco Elver <elver@xxxxxxxxxx>
> > Date: Thu Apr 8 12:36:01 2021 +0200
> > perf: Add support for SIGTRAP on perf events
> > ...
> > [ 52.848925] BUG: scheduling while atomic: perf/6549/0x00000002
> Had bf9ad37dc8a not been reverted due to insufficient beauty, you could
> trivially make the sigtrap test a happy camper (wart tested in tip-rt).
Yeah, I cherry-picked bf9ad37dc8a:
Author: Oleg Nesterov <oleg@xxxxxxxxxx>
Date: Tue Jul 14 14:26:34 2015 +0200
signal, x86: Delay calling signals in atomic on RT enabled kernels
Applied your force_sig_delayed() call to send_sig_perf() and got:
[root@nine ~]# perf test sigtrap
73: Sigtrap : Ok
[root@nine ~]#
Happy camper indeed.
[acme@nine linux]$ git log --oneline -5
24f75a478a32 (HEAD) signal, x86: Delay calling signals in atomic on RT enabled kernels
d37d728e9a66 (tag: v6.4-rt6, linux-rt-devel/linux-6.4.y-rt) v6.4-rt6
4d1139baae8b mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save().
dc93c1f07d48 seqlock: Do the lockdep annotation before locking in do_write_seqcount_begin_nested()
a3f6be6e5353 printk: Check only for migration in printk_deferred_*().
[acme@nine linux]$ git diff
diff --git a/kernel/signal.c b/kernel/signal.c
index 464e68a8a273..f186e0d85381 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1868,6 +1868,9 @@ int send_sig_perf(void __user *addr, u32 type, u64 sig_data)
TRAP_PERF_FLAG_ASYNC :
0;
+ if (force_sig_delayed(&info, current))
+ return 0;
+
return send_sig_info(info.si_signo, &info, current);
}
[acme@nine linux]$ uname -a
Linux nine 6.4.0-rt6+ #3 SMP PREEMPT_RT Wed Jul 26 11:46:12 -03 2023 x86_64 x86_64 x86_64 GNU/Linux
[acme@nine linux]$ perf test sigtrap
71: Sigtrap : Ok
[acme@nine linux]$
- Arnaldo
> @@ -1829,6 +1869,9 @@ int send_sig_perf(void __user *addr, u32
> TRAP_PERF_FLAG_ASYNC :
> 0;
>
> + if (force_sig_delayed(&info, current))
> + return 0;
> +
> return send_sig_info(info.si_signo, &info, current);
> }
