From: Thomas Gleixner <tglx@linutronix.de>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Clark Williams <williams@redhat.com>,
Juri Lelli <juri.lelli@gmail.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: WARN_ON: userstacktrace on irq events
Date: Fri, 5 Apr 2019 10:12:27 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.1904051000290.1802@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20190403121640.70128095@gandalf.local.home>
On Wed, 3 Apr 2019, Steven Rostedt wrote:
> Juri reported this from the -rt kernel, but I can easily trigger it in
> mainline. By simply doing:
>
> # cd /sys/kernel/tracing
> # echo 1 > options/userstacktrace
> # echo 1 > events/irq/enable
> This is simply caused by the irq trace events doing a user stack trace:
>
> ftrace_trace_userstack {
> save_stack_trace_user {
> __save_stack_trace_user {
> copy_stack_frame {
> access_ok {
> WARN_ON_IN_IRQ()
>
> BOOM! Warn on.
>
> Can we make that access_ok() call in the copy_stack_frame not trigger
> the warning just if we are in an interrupt?
You really want to have access_ok_atomic() or such which does not have the
WARN and use that in copy_stack_frame(). That's fine here because the
actual copy is inside a pagefault disabled region.
Thanks,
tglx
next prev parent reply other threads:[~2019-04-05 8:12 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-03 16:16 WARN_ON: userstacktrace on irq events Steven Rostedt
2019-04-05 8:12 ` Thomas Gleixner [this message]
2019-04-05 13:32 ` Steven Rostedt
2019-06-21 14:12 ` Masami Hiramatsu
2019-07-22 8:32 ` [PATCH 0/1] x86/stacktrace: Fix userstacktrace access_ok() WARNING in " Eiichi Tsukata
2019-07-22 8:32 ` [PATCH 1/1] " Eiichi Tsukata
2019-07-22 8:46 ` [tip:x86/urgent] x86/stacktrace: Prevent access_ok() warnings in arch_stack_walk_user() tip-bot for Eiichi Tsukata
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