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 <olivier@xxxxxxxxxxxxxx>
> ---
> 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 <linux/init.h>
> #include <linux/errno.h>
> #include <linux/sched/signal.h>
> -#include <linux/mm.h>
> -#include <linux/sched/mm.h>
> #include <linux/percpu.h>
> #include <linux/slab.h>
> #include <linux/rculist_nulls.h>
> @@ -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
