linux-kernel - Re: [PATCH 2/2] locking: Apply contention tracepoints in the slow path

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YjSBRNxzaE9c+F/1@boqun-archlinux>
Date:   Fri, 18 Mar 2022 20:55:32 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Byungchul Park <byungchul.park@....com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Arnd Bergmann <arnd@...db.de>,
        Radoslaw Burny <rburny@...gle.com>, linux-arch@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH 2/2] locking: Apply contention tracepoints in the slow
 path

On Wed, Mar 16, 2022 at 03:45:48PM -0700, Namhyung Kim wrote:
[...]
> @@ -209,6 +210,7 @@ static inline int __sched __down_common(struct semaphore *sem, long state,
>  								long timeout)
>  {
>  	struct semaphore_waiter waiter;
> +	bool tracing = false;
>  
>  	list_add_tail(&waiter.list, &sem->wait_list);
>  	waiter.task = current;
> @@ -220,18 +222,28 @@ static inline int __sched __down_common(struct semaphore *sem, long state,
>  		if (unlikely(timeout <= 0))
>  			goto timed_out;
>  		__set_current_state(state);
> +		if (!tracing) {
> +			trace_contention_begin(sem, 0);

This looks a littl ugly ;-/ Maybe we can rename __down_common() to
___down_common() and implement __down_common() as:

	static inline int __sched __down_common(...)
	{
		int ret;
		trace_contention_begin(sem, 0);
		ret = ___down_common(...);
		trace_contention_end(sem, ret);
		return ret;
	}

Thoughts?

Regards,
Boqun

> +			tracing = true;
> +		}
>  		raw_spin_unlock_irq(&sem->lock);
>  		timeout = schedule_timeout(timeout);
>  		raw_spin_lock_irq(&sem->lock);
> -		if (waiter.up)
> +		if (waiter.up) {
> +			trace_contention_end(sem, 0);
>  			return 0;
> +		}
>  	}
>  
>   timed_out:
> +	if (tracing)
> +		trace_contention_end(sem, -ETIME);
>  	list_del(&waiter.list);
>  	return -ETIME;
>  
>   interrupted:
> +	if (tracing)
> +		trace_contention_end(sem, -EINTR);
>  	list_del(&waiter.list);
>  	return -EINTR;
>  }
> -- 
> 2.35.1.894.gb6a874cedc-goog
>