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From:   Jens Axboe <axboe@kernel.dk>
To:     io-uring@vger.kernel.org
Cc:     torvalds@linux-foundation.org, ebiederm@xmission.com,
        metze@samba.org, oleg@redhat.com, linux-kernel@vger.kernel.org,
        Jens Axboe <axboe@kernel.dk>
Subject: [PATCH 1/8] io_uring: handle signals for IO threads like a normal thread
Date:   Thu, 25 Mar 2021 18:39:24 -0600
Message-Id: <20210326003928.978750-2-axboe@kernel.dk>
In-Reply-To: <20210326003928.978750-1-axboe@kernel.dk>
References: <20210326003928.978750-1-axboe@kernel.dk>
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We go through various hoops to disallow signals for the IO threads, but
there's really no reason why we cannot just allow them. The IO threads
never return to userspace like a normal thread, and hence don't go through
normal signal processing. Instead, just check for a pending signal as part
of the work loop, and call get_signal() to handle it for us if anything
is pending.

With that, we can support receiving signals, including special ones like
SIGSTOP.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io-wq.c    | 21 +++++++++++++++++----
 fs/io_uring.c | 10 ++++++++--
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index b7c1fa932cb3..2dbdc552f3ba 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -505,8 +505,14 @@ static int io_wqe_worker(void *data)
 		ret = schedule_timeout(WORKER_IDLE_TIMEOUT);
 		if (try_to_freeze() || ret)
 			continue;
-		if (fatal_signal_pending(current))
-			break;
+		if (signal_pending(current)) {
+			struct ksignal ksig;
+
+			if (fatal_signal_pending(current))
+				break;
+			get_signal(&ksig);
+			continue;
+		}
 		/* timed out, exit unless we're the fixed worker */
 		if (test_bit(IO_WQ_BIT_EXIT, &wq->state) ||
 		    !(worker->flags & IO_WORKER_F_FIXED))
@@ -715,8 +721,15 @@ static int io_wq_manager(void *data)
 		io_wq_check_workers(wq);
 		schedule_timeout(HZ);
 		try_to_freeze();
-		if (fatal_signal_pending(current))
-			set_bit(IO_WQ_BIT_EXIT, &wq->state);
+		if (signal_pending(current)) {
+			struct ksignal ksig;
+
+			if (fatal_signal_pending(current))
+				set_bit(IO_WQ_BIT_EXIT, &wq->state);
+			else
+				get_signal(&ksig);
+			continue;
+		}
 	} while (!test_bit(IO_WQ_BIT_EXIT, &wq->state));
 
 	io_wq_check_workers(wq);
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 54ea561db4a5..3a9d021db328 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6765,8 +6765,14 @@ static int io_sq_thread(void *data)
 			timeout = jiffies + sqd->sq_thread_idle;
 			continue;
 		}
-		if (fatal_signal_pending(current))
-			break;
+		if (signal_pending(current)) {
+			struct ksignal ksig;
+
+			if (fatal_signal_pending(current))
+				break;
+			get_signal(&ksig);
+			continue;
+		}
 		sqt_spin = false;
 		cap_entries = !list_is_singular(&sqd->ctx_list);
 		list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
-- 
2.31.0