Re: [PATCH 1/3] perf: Rollback callchain buffer refcount under thecallchain mutex

[Jiri Olsa]

On Fri, Aug 02, 2013 at 06:29:54PM +0200, Frederic Weisbecker wrote:
> When we fail to allocate the callchain buffers, we rollback the refcount
> we did and return from get_callchain_buffers().
> 
> However we take the refcount and allocate under the callchain lock
> but the rollback is done outside the lock.
> 
> As a result, while we rollback, some concurrent callchain user may
> call get_callchain_buffers(), see the non-zero refcount and give up
> because the buffers are NULL without itself retrying the allocation.
> 
> The consequences aren't that bad but that behaviour looks weird enough and
> it's better to give their chances to the following callchain users where
> we failed.
> 
> Reported-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>

Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
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