linux-kernel - Re: [PATCH] timer: silenct a lockdep splat with debugobjects

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Message-ID: <20200313201314.GE5086@worktop.programming.kicks-ass.net>
Date:   Fri, 13 Mar 2020 21:13:14 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Qian Cai <cai@....pw>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        John Stultz <john.stultz@...aro.org>, sboyd@...nel.org,
        rostedt@...dmis.org, hannes@...xchg.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] timer: silenct a lockdep splat with debugobjects

On Fri, Mar 13, 2020 at 03:32:52PM -0400, Qian Cai wrote:
> Well, in mm/vmstat.c (init_mm_internals) case for example, it was initialized
> as a static,
> 
> static DECLARE_DEFERRABLE_WORK(shepherd, vmstat_shepherd);
> 
> which will not call __debug_object_init(). 

Then fix that.

That is, all of:

  DECLARE_DEFERRABLE_WORK
  KTHREAD_DELAYED_WORK_INIT
  DEFINE_TIMER

are broken and need to go.

Unless of course, you can frob debugobjects such that we can provide the
required storage through is_static_object() and modify the above static
declarators to provide the storage.

Or, fix that random crud to do the wakeup outside of the lock.

Plenty options..