[PATCH] io_uring: don't use {test,clear}_tsk_thread_flag() for current

[Jens Axboe <axboe@kernel.dk>]

Linus correctly points out that this is both unnecessary and generates
much worse code on some archs as going from current to thread_info is
actually backwards - and obviously just wasteful, since the thread_info
is what we care about.

Since io_uring only operates on current for these operations, just use
test_thread_flag() instead. For io-wq, we can further simplify and use
tracehook_notify_signal() to handle the TIF_NOTIFY_SIGNAL work and clear
the flag. The latter isn't an actual bug right now, but it may very well
be in the future if we place other work items under TIF_NOTIFY_SIGNAL.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/io-uring/CAHk-=wgYhNck33YHKZ14mFB5MzTTk8gqXHcfj=RWTAXKwgQJgg@mail.gmail.com/
Signed-off-by: Jens Axboe <axboe@kernel.dk>

---

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 3dc10bfd8c3b..2dd43bdb9c7b 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -388,11 +388,9 @@ static struct io_wq_work *io_get_next_work(struct io_wqe *wqe)
 
 static bool io_flush_signals(void)
 {
-	if (unlikely(test_tsk_thread_flag(current, TIF_NOTIFY_SIGNAL))) {
+	if (unlikely(test_thread_flag(TIF_NOTIFY_SIGNAL))) {
 		__set_current_state(TASK_RUNNING);
-		if (current->task_works)
-			task_work_run();
-		clear_tsk_thread_flag(current, TIF_NOTIFY_SIGNAL);
+		tracehook_notify_signal();
 		return true;
 	}
 	return false;
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 543551d70327..be04bc6b5b99 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6873,7 +6873,7 @@ static int io_run_task_work_sig(void)
 		return 1;
 	if (!signal_pending(current))
 		return 0;
-	if (test_tsk_thread_flag(current, TIF_NOTIFY_SIGNAL))
+	if (test_thread_flag(TIF_NOTIFY_SIGNAL))
 		return -ERESTARTSYS;
 	return -EINTR;
 }

-- 
Jens Axboe