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Thu, 27 May 2021 06:46:42 -0700 (PDT) Subject: Re: [PATCH] io_uring: handle signals before letting io-worker exit To: Olivier Langlois , Pavel Begunkov , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: <60ae94d1.1c69fb81.94f7a.2a35SMTPIN_ADDED_MISSING@mx.google.com> From: Jens Axboe Message-ID: <3d1bd9e2-b711-0aac-628e-89b95ff8dbc3@kernel.dk> Date: Thu, 27 May 2021 07:46:44 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <60ae94d1.1c69fb81.94f7a.2a35SMTPIN_ADDED_MISSING@mx.google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 5/26/21 12:21 PM, Olivier Langlois wrote: > This is required for proper core dump generation. > > Because signals are normally serviced before resuming userspace and an > io_worker thread will never resume userspace, it needs to explicitly > call the signal servicing functions. > > Also, notice that it is possible to exit from the io_wqe_worker() > function main loop while having a pending signal such as when > the IO_WQ_BIT_EXIT bit is set. > > It is crucial to service any pending signal before calling do_exit() > Proper coredump generation is relying on PF_SIGNALED to be set. > > More specifically, exit_mm() is using this flag to wait for the > core dump completion before releasing its memory descriptor. > > Signed-off-by: Olivier Langlois > --- > fs/io-wq.c | 22 ++++++++++++++++++++-- > 1 file changed, 20 insertions(+), 2 deletions(-) > > diff --git a/fs/io-wq.c b/fs/io-wq.c > index 5361a9b4b47b..b76c61e9aff2 100644 > --- a/fs/io-wq.c > +++ b/fs/io-wq.c > @@ -9,8 +9,6 @@ > #include > #include > #include > -#include > -#include > #include > #include > #include > @@ -193,6 +191,26 @@ static void io_worker_exit(struct io_worker *worker) > > kfree_rcu(worker, rcu); > io_worker_ref_put(wqe->wq); > + /* > + * Because signals are normally serviced before resuming userspace and an > + * io_worker thread will never resume userspace, it needs to explicitly > + * call the signal servicing functions. > + * > + * Also notice that it is possible to exit from the io_wqe_worker() > + * function main loop while having a pending signal such as when > + * the IO_WQ_BIT_EXIT bit is set. > + * > + * It is crucial to service any pending signal before calling do_exit() > + * Proper coredump generation is relying on PF_SIGNALED to be set. > + * > + * More specifically, exit_mm() is using this flag to wait for the > + * core dump completion before releasing its memory descriptor. > + */ > + if (signal_pending(current)) { > + struct ksignal ksig; > + > + get_signal(&ksig); > + } > do_exit(0); > } Do we need the same thing in fs/io_uring.c:io_sq_thread()? -- Jens Axboe