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From: "Kohli, Gaurav" <>
To: Tejun Heo <>
Subject: Re: [PATCH] percpu_counter: Remove debug_object_free call twice
Date: Mon, 27 Aug 2018 12:26:32 +0530	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Hi ,

Sorry for very late reminder, just wanted to know is below understanding 
of code is wrong?


On 4/17/2018 11:59 AM, Kohli, Gaurav wrote:
> On 4/17/2018 3:18 AM, Tejun Heo wrote:
>> On Fri, Apr 13, 2018 at 03:05:03PM +0530, Gaurav Kohli wrote:
>>> During percpu_counter destroy, debug_object_free is calling
>>> twice which may create race. So removing once instance of call
>>> from debug_percpu_counter_deactivate.
>> I don't quite follow.  Can you please elaborate how it can be called
>> twice?
> Hi Tejun,
> In percpu_counter_fixup_free function, first call is 
> percpu_counter_destroy -> debug_percpu_counter_deactivate (this will set 
> inactive and free the debug object as well for percpu counter) -> 
> free_percpu (finally freeing the counters).
> Below is the code snippet:
>          case DEBUG_STATE_ACTIVE:
>                  percpu_counter_destroy(fbc); -> first call
>                  debug_object_free(fbc, &percpu_counter_debug_descr); -> 
> this will again call the same debug object free, if somehow counters 
> will reinitialize between these two calls.
> We are seeing one race condition issue where one object of db list is 
> corrupted and just before object of that corrupted node is 
> percpu_counter, Still i am not sure the reason of race as it is very
> difficult to reproduce. But i have found this during code review. Please 
> correct me, if i misunderstood this.
>> Thanks.

Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, 
Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.

      reply	other threads:[~2018-08-27  6:56 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-13  9:35 [PATCH] percpu_counter: Remove debug_object_free call twice Gaurav Kohli
2018-04-16 21:48 ` Tejun Heo
2018-04-17  6:29   ` Kohli, Gaurav
2018-08-27  6:56     ` Kohli, Gaurav [this message]

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