linux-kernel - Re: [PATCH 2/2 v3] lib: debugobjects: touch watchdog to avoid softlockup when !CONFIG

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Message-ID: <20180118150505.GD2249@hirez.programming.kicks-ass.net>
Date:   Thu, 18 Jan 2018 16:05:05 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Yang Shi <yang.s@...baba-inc.com>, longman@...hat.com,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2 v3] lib: debugobjects: touch watchdog to avoid
 softlockup when !CONFIG_PREEMPT

On Thu, Jan 18, 2018 at 10:02:25AM +0100, Thomas Gleixner wrote:
> > >   2) We can do a cond_resched() if not in atomic context and interrupts are
> > >      enabled.
> > 
> > I did try this before I went with touching softlockup watchdog approach. The
> > problem is in_atomic() can't tell if it is in atomic context on non-preempt
> > kernel. For preempt kernel, it is easy.
> 
> Peter, can we do anything about that?

Not really :/ Take for instance a spinlock on !PREEMPT, only the lock
variable is touched, preempt_count isn't. So we cannot know.