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From: Thomas Gleixner <tglx@linutronix.de>
To: Oleg Nesterov <oleg@redhat.com>
Cc: John Stultz <jstultz@google.com>, Marco Elver <elver@google.com>, Peter
 Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>, "Eric W.
 Biederman" <ebiederm@xmission.com>, linux-kernel@vger.kernel.org,
 linux-kselftest@vger.kernel.org, Dmitry Vyukov <dvyukov@google.com>,
 kasan-dev@googlegroups.com, Edward Liaw <edliaw@google.com>, Carlos Llamas
 <cmllamas@google.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH v6 1/2] posix-timers: Prefer delivery of signals to the
 current thread
In-Reply-To: <20240403150343.GC31764@redhat.com>
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 <874jcid3f6.ffs@tglx> <20240403150343.GC31764@redhat.com>
Date: Wed, 03 Apr 2024 17:43:32 +0200
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On Wed, Apr 03 2024 at 17:03, Oleg Nesterov wrote:
> On 04/03, Thomas Gleixner wrote:
>> The test if fragile as hell as there is absolutely no guarantee that the
>> signal target distribution is as expected. The expectation is based on a
>> statistical assumption which does not really hold.
>
> Agreed. I too never liked this test-case.
>
> I forgot everything about this patch and test-case, I can't really read
> your patch right now (sorry), so I am sure I missed something, but
>
>>  static void *distribution_thread(void *arg)
>>  {
>> -	while (__atomic_load_n(&remain, __ATOMIC_RELAXED));
>> -	return NULL;
>> +	while (__atomic_load_n(&remain, __ATOMIC_RELAXED) && !done) {
>> +		if (got_signal)
>> +			usleep(10);
>> +	}
>> +
>> +	return (void *)got_signal;
>>  }
>
> Why distribution_thread() can't simply exit if got_signal != 0 ?
>
> See https://lore.kernel.org/all/20230128195641.GA14906@redhat.com/

Indeed. It's too obvious :)