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Message-ID: <20240308141311.03eefef1@gandalf.local.home>
Date: Fri, 8 Mar 2024 14:13:11 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mark Rutland
<mark.rutland@....com>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Andrew Morton <akpm@...ux-foundation.org>, Linus Torvalds
<torvalds@...ux-foundation.org>, joel@...lfernandes.org, linke li
<lilinke99@...com>, Rabin Vincent <rabin@....in>, stable@...r.kernel.org
Subject: Re: [PATCH 4/6] tracing: Fix waking up tracing readers
On Fri, 08 Mar 2024 13:38:20 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:
> +static DEFINE_MUTEX(wait_mutex);
> +
> +static bool wait_woken_prepare(struct trace_iterator *iter, int *wait_index)
> +{
> + bool woken = false;
> +
> + mutex_lock(&wait_mutex);
> + if (iter->waking)
> + woken = true;
> + *wait_index = iter->wait_index;
> + mutex_unlock(&wait_mutex);
> +
> + return woken;
> +}
The last patch adds this code after a prepare_to_wait(), which triggered
the warning:
do not call blocking ops when !TASK_RUNNING; state=1 set at [<00000000797e3e20>] prepare_to_wait+0x48/0xf0
Which is correct. The prepare_to_wait() set task state to
TASK_INTERRUPTIBLE, so I can not call a mutex after that.
I'll send a v2 where I switch this over to spin locks.
-- Steve
> +
> +static bool wait_woken_check(struct trace_iterator *iter, int *wait_index)
> +{
> + bool woken = false;
> +
> + mutex_lock(&wait_mutex);
> + if (iter->waking || *wait_index != iter->wait_index)
> + woken = true;
> + mutex_unlock(&wait_mutex);
> +
> + return woken;
> +}
> +
> +static void wait_woken_set(struct trace_iterator *iter)
> +{
> + mutex_lock(&wait_mutex);
> + iter->waking++;
> + iter->wait_index++;
> + mutex_unlock(&wait_mutex);
> +}
> +
> +static void wait_woken_clear(struct trace_iterator *iter)
> +{
> + mutex_lock(&wait_mutex);
> + iter->waking--;
> + mutex_unlock(&wait_mutex);
> +}
> +
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