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From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: syzbot <syzbot+53f8ce8bbc07924b6417@syzkaller.appspotmail.com>,
	linux-kernel@vger.kernel.org, mingo@redhat.com,
	syzkaller-bugs@googlegroups.com
Subject: Re: BUG: using __this_cpu_read() in preemptible code in trace_hardirqs_on
Date: Fri, 23 Oct 2020 10:18:47 +0200	[thread overview]
Message-ID: <20201023081847.GO2611@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201022163247.5bb93ab3@gandalf.local.home>

On Thu, Oct 22, 2020 at 04:32:47PM -0400, Steven Rostedt wrote:
> On Thu, 22 Oct 2020 12:30:28 +0200
> Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > Subject: lockdep: Fix preemption WARN for spurious IRQ-enable
> > From: Peter Zijlstra <peterz@infradead.org>
> > Date: Thu Oct 22 12:23:02 CEST 2020
> > 
> > It is valid (albeit uncommon) to call local_irq_enable() without first
> > having called local_irq_disable(). In this case we enter
> > lockdep_hardirqs_on*() with IRQs enabled and trip a preemption warning
> > for using __this_cpu_read().
> > 
> > Use this_cpu_read() instead to avoid the warning.
> 
> I was wondering why you were using __this_cpu_read() in the first place.

Well, because all other sites are actually with IRQs disabled :/ It's
just this spurious enable thing that's an exception.

> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Thanks!

  reply	other threads:[~2020-10-23  8:19 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-13 11:22 BUG: using __this_cpu_read() in preemptible code in trace_hardirqs_on syzbot
2020-10-13 13:17 ` Steven Rostedt
2020-10-21 13:17   ` Peter Zijlstra
2020-10-21 14:34     ` Steven Rostedt
2020-10-21 15:12       ` Peter Zijlstra
2020-10-21 15:27         ` Steven Rostedt
2020-10-22 10:30           ` Peter Zijlstra
2020-10-22 20:32             ` Steven Rostedt
2020-10-23  8:18               ` Peter Zijlstra [this message]
2020-10-16 17:16 ` syzbot
2020-10-16 20:33 ` syzbot
2020-10-21 13:09   ` Dmitry Vyukov

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