linux-kernel - Re: [PATCH] uprobes: Remove redundant spinlock in uprobe_deny

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Message-ID: <20240731141231.GB16718@redhat.com>
Date: Wed, 31 Jul 2024 16:12:32 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Liao Chang <liaochang1@...wei.com>
Cc: peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
	namhyung@...nel.org, mark.rutland@....com,
	alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
	irogers@...gle.com, adrian.hunter@...el.com,
	kan.liang@...ux.intel.com, mhiramat@...nel.org,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] uprobes: Remove redundant spinlock in uprobe_deny_signal

On 07/31, Liao Chang wrote:
>
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1979,9 +1979,7 @@ bool uprobe_deny_signal(void)
>  	WARN_ON_ONCE(utask->state != UTASK_SSTEP);
>  
>  	if (task_sigpending(t)) {
> -		spin_lock_irq(&t->sighand->siglock);
>  		clear_tsk_thread_flag(t, TIF_SIGPENDING);
> -		spin_unlock_irq(&t->sighand->siglock);

Agreed, in this case ->siglock buys nothing, another signal can come
right after spin_unlock().

Acked-by: Oleg Nesterov <oleg@...hat.com>