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io_uring: fix regression with always ignoring signals in io_cqring_wait() 

When switching to TWA_SIGNAL for task_work notifications, we also made
any signal based condition in io_cqring_wait() return -ERESTARTSYS.
This breaks applications that rely on using signals to abort someone
waiting for events.

Check if we have a signal pending because of queued task_work, and
repeat the signal check once we've run the task_work. This provides a
reliable way of telling the two apart.

Additionally, only use TWA_SIGNAL if we are using an eventfd. If not,
we don't have the dependency situation described in the original commit,
and we can get by with just using TWA_RESUME like we previously did.

Fixes: ce593a6c48 ("io_uring: use signal based task_work running")
Cc: stable@vger.kernel.org # v5.7
Reported-by: Andres Freund <andres@anarazel.de>
Tested-by: Andres Freund <andres@anarazel.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2020-07-04 08:55:50 -06:00
parent ce593a6c48
commit b7db41c9e0
1 changed files with 22 additions and 7 deletions
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29
fs/io_uring.c
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@ -4072,14 +4072,22 @@ struct io_poll_table {
int error;
};
static int io_req_task_work_add(struct io_kiocb *req, struct callback_head *cb,
int notify)
static int io_req_task_work_add(struct io_kiocb *req, struct callback_head *cb)
{
struct task_struct *tsk = req->task;
int ret;
struct io_ring_ctx *ctx = req->ctx;
int ret, notify = TWA_RESUME;
if (req->ctx->flags & IORING_SETUP_SQPOLL)
/*
* SQPOLL kernel thread doesn't need notification, just a wakeup.
* If we're not using an eventfd, then TWA_RESUME is always fine,
* as we won't have dependencies between request completions for
* other kernel wait conditions.
*/
if (ctx->flags & IORING_SETUP_SQPOLL)
notify = 0;
else if (ctx->cq_ev_fd)
notify = TWA_SIGNAL;
ret = task_work_add(tsk, cb, notify);
if (!ret)
@ -4110,7 +4118,7 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll,
* of executing it. We can't safely execute it anyway, as we may not
* have the needed state needed for it anyway.
*/
ret = io_req_task_work_add(req, &req->task_work, TWA_SIGNAL);
ret = io_req_task_work_add(req, &req->task_work);
if (unlikely(ret)) {
WRITE_ONCE(poll->canceled, true);
tsk = io_wq_get_task(req->ctx->io_wq);
@ -6201,7 +6209,14 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
if (current->task_works)
task_work_run();
if (signal_pending(current)) {
ret = -ERESTARTSYS;
if (current->jobctl & JOBCTL_TASK_WORK) {
spin_lock_irq(&current->sighand->siglock);
current->jobctl &= ~JOBCTL_TASK_WORK;
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
continue;
}
ret = -EINTR;
break;
}
if (io_should_wake(&iowq, false))
@ -6210,7 +6225,7 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
} while (1);
finish_wait(&ctx->wait, &iowq.wq);
restore_saved_sigmask_unless(ret == -ERESTARTSYS);
restore_saved_sigmask_unless(ret == -EINTR);
return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0;
}