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From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Qais Yousef <qais.yousef@arm.com>
Cc: Petr Mladek <pmladek@suse.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Steven Rostedt <rostedt@goodmis.org>,
	John Ogness <john.ogness@linutronix.de>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/2] Fix BUG: Invalid wait context in hrtimer_interrupt()
Date: Tue, 26 Jan 2021 13:46:19 +0900	[thread overview]
Message-ID: <YA+em8XkTidYetGE@jagdpanzerIV.localdomain> (raw)
In-Reply-To: <20210123233741.3614408-1-qais.yousef@arm.com>

On (21/01/23 23:37), Qais Yousef wrote:
> 
> I hit a pr_warn() inside hrtimer_interrupt() which lead to a BUG: Invalid wait
> context splat.
> 
> The problem wasn't reproducible but I think the cause is obvious, printk can't
> be called from interrupt context.
> 
> AFAICU printk_deferred() is safe from NMI, so I assumed it is safe to be called
> from hrtimer_interrupt() too. Adding a pr_warn_once() inside
> hrtimer_interrupt() in a location where it is always hit produces the BUG
> splat. Replacing it with pr_warn_deferred_once() generates the printk warning
> without any splat.

Could you please post the lockdep splat?
Why is it invalid? Is this... -rt kernel, perhaps?

	-ss

  parent reply	other threads:[~2021-01-26 23:17 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-23 23:37 [PATCH 0/2] Fix BUG: Invalid wait context in hrtimer_interrupt() Qais Yousef
2021-01-23 23:37 ` [PATCH 1/2] printk: Add new pr_*_deferred_once() variants Qais Yousef
2021-01-25 10:37   ` Peter Zijlstra
2021-01-25 10:58     ` John Ogness
2021-01-25 19:46       ` Qais Yousef
2022-01-11 13:40       ` Andy Shevchenko
2022-01-13 11:20         ` Qais Yousef
2021-01-23 23:37 ` [PATCH 2/2] hrtimer: Use pr_warn_deferred_once() in hrtimer_interrupt() Qais Yousef
2021-01-26  4:46 ` Sergey Senozhatsky [this message]
2021-01-26 14:59   ` [PATCH 0/2] Fix BUG: Invalid wait context " Qais Yousef
2021-01-26 15:22     ` John Ogness
2021-01-26 16:18       ` Peter Zijlstra
2021-01-26 15:58     ` Sergey Senozhatsky
2021-01-26 16:23       ` Peter Zijlstra
2021-01-26 18:08         ` Qais Yousef
2021-01-26 16:58       ` Petr Mladek

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