linux-kernel - Re: [PATCH 1/3] perf: convert perf_event_context.refcount to refcount

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Message-ID: <20190129093748.GF28467@hirez.programming.kicks-ass.net>
Date:   Tue, 29 Jan 2019 10:37:48 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Elena Reshetova <elena.reshetova@...el.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...hat.com, acme@...nel.org,
        namhyung@...nel.org, alexander.shishkin@...ux.intel.com,
        jolsa@...hat.com, keescook@...omium.org, tglx@...utronix.de
Subject: Re: [PATCH 1/3] perf: convert perf_event_context.refcount to
 refcount_t

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.