linux-kernel - Re: [PATCH 2/2] ksefltest: pidfd: Fix wait

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Message-ID: <20211029083248.7vttuxbwbtdylrnq@wittgenstein>
Date:   Fri, 29 Oct 2021 10:32:48 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Li Zhijian <lizhijian@...fujitsu.com>
Cc:     linux-kselftest@...r.kernel.org, shuah@...nel.org,
        linux-kernel@...r.kernel.org,
        Christian Brauner <christian@...uner.io>,
        Philip Li <philip.li@...el.com>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH 2/2] ksefltest: pidfd: Fix wait_states: Test terminated
 by timeout

On Fri, Oct 29, 2021 at 10:45:28AM +0800, Li Zhijian wrote:
> 0Day/LKP observed that the kselftest blocks foever since one of the
> pidfd_wait doesn't terminate in 1 of 30 runs. After digging into
> the source, we found that it blocks at:
> ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WCONTINUED, NULL), 0);
> 
> we can reproduce it by:
> $ while true; do make run_tests -C pidfd; done
> 
> a delay to ensure that the parent can see child process WCONTINUED.
> 
> CC: Christian Brauner <christian@...uner.io>
> CC: Shuah Khan <shuah@...nel.org>
> CC: Philip Li <philip.li@...el.com>
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Li Zhijian <lizhijian@...fujitsu.com>
> ---

Not a fan of the usleep() solution but if it fixes it it's fine for
a test, I think.
Acked-by: Christian Brauner <christian.brauner@...ntu.com>