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Date:   Tue, 29 Jan 2019 10:37:48 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Elena Reshetova <elena.reshetova@intel.com>
Cc:     linux-kernel@vger.kernel.org, mingo@redhat.com, acme@kernel.org,
        namhyung@kernel.org, alexander.shishkin@linux.intel.com,
        jolsa@redhat.com, keescook@chromium.org, tglx@linutronix.de
Subject: Re: [PATCH 1/3] perf: convert perf_event_context.refcount to
 refcount_t
Message-ID: <20190129093748.GF28467@hirez.programming.kicks-ass.net>
References: <1548678448-24458-1-git-send-email-elena.reshetova@intel.com>
 <1548678448-24458-2-git-send-email-elena.reshetova@intel.com>
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On Mon, Jan 28, 2019 at 02:27:26PM +0200, Elena Reshetova wrote:
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 3cd13a3..a1e87d2 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -1171,7 +1171,7 @@ static void perf_event_ctx_deactivate(struct perf_event_context *ctx)
>  
>  static void get_ctx(struct perf_event_context *ctx)
>  {
> -	WARN_ON(!atomic_inc_not_zero(&ctx->refcount));
> +	WARN_ON(!refcount_inc_not_zero(&ctx->refcount));

This could be refcount_inc(), remember how that already produces a WARN
when we try and increment 0.