From: Peter Zijlstra <peterz@infradead.org>
To: Jules Irenge <jbi.octave@gmail.com>
Cc: linux-kernel@vger.kernel.org, boqun.feng@gmail.com,
Thomas Gleixner <tglx@linutronix.de>,
Jiri Kosina <jkosina@suse.cz>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Ingo Molnar <mingo@kernel.org>, Qian Cai <cai@lca.pw>,
Eiichi Tsukata <devel@etsukata.com>,
Pavankumar Kondeti <pkondeti@codeaurora.org>,
Arnd Bergmann <arnd@arndb.de>,
Tyler Hicks <tyhicks@canonical.com>
Subject: Re: [PATCH 1/1] cpu: Add annotation inside clear_tasks_mm_cpumask()
Date: Thu, 16 Apr 2020 00:25:45 +0200 [thread overview]
Message-ID: <20200415222545.GN2483@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20200415184937.32373-2-jbi.octave@gmail.com>
On Wed, Apr 15, 2020 at 07:49:37PM +0100, Jules Irenge wrote:
> Sparse reports a warning
>
> warning: context imbalance in clear_tasks_mm_cpumask() - different lock contexts for basic block
Does this sparse crap actually ever catch a real problem, or does it
only result in horrible code like this?
> The root cause is the missing annotation inside clear_tasks_mm_cpumask()
>
> Add the missing __acquire(&t->alloc_lock) annotation.
That's just wrong; the actual cause is find_lock_task_mm() not being
annotated, and the reason for that is because __cond_lock() is a
horrible piece of crap.
Barring any evidence that these annotations actually help anybody, can't
we just remove it all instead of making an ever bigger mess of things?
> Signed-off-by: Jules Irenge <jbi.octave@gmail.com>
> ---
> kernel/cpu.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index 9c706af713fb..d8c452a8dd09 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -834,6 +834,7 @@ void clear_tasks_mm_cpumask(int cpu)
> t = find_lock_task_mm(p);
> if (!t)
> continue;
> + __acquire(&t->alloc_lock);
> cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
> task_unlock(t);
> }
> --
> 2.24.1
>
prev parent reply other threads:[~2020-04-15 22:26 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-15 18:49 [PATCH 0/1] Fix context imbalance warning Jules Irenge
2020-04-15 18:49 ` [PATCH 1/1] cpu: Add annotation inside clear_tasks_mm_cpumask() Jules Irenge
2020-04-15 22:25 ` Peter Zijlstra [this message]
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