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From: Roman Penyaev <rpenyaev@suse.de>
To: unlisted-recipients:; (no To-header on input)
Cc: Roman Penyaev <rpenyaev@suse.de>,
	Davidlohr Bueso <dbueso@suse.de>, Jason Baron <jbaron@akamai.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 1/1] epoll: remove wrong assert that ep_poll_callback is always called with irqs off
Date: Tue,  8 Jan 2019 11:01:21 +0100	[thread overview]
Message-ID: <20190108100121.20247-1-rpenyaev@suse.de> (raw)

That was wrong assumption that all drivers disable irqs before waking up
a wait queue.  Even assert line is removed the whole logic stays correct:
epoll always locks rwlock with irqs disabled and by itself does not call
from interrupts, thus it is up to driver how to call wake_up_locked(),
because if driver does not handle any interrupts (like fuse in the the
report) of course it is safe on its side to take a simple spin_lock.

Signed-off-by: Roman Penyaev <rpenyaev@suse.de>
Reported-by: syzbot+aea82bf9ee6ffd9a79d9@syzkaller.appspotmail.com
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 fs/eventpoll.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index f307c8679027..f5f88250cdf2 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1217,12 +1217,6 @@ static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, v
 	__poll_t pollflags = key_to_poll(key);
 	int ewake = 0;
 
-	/*
-	 * Called by irq context or interrupts are disabled by the wake_up_*poll
-	 * callers.
-	 */
-	lockdep_assert_irqs_disabled();
-
 	read_lock(&ep->lock);
 
 	ep_set_busy_poll_napi_id(epi);
-- 
2.19.1


             reply	other threads:[~2019-01-08 10:01 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-08 10:01 Roman Penyaev [this message]
2019-01-08 12:42 ` Roman Penyaev
2019-01-08 15:16   ` Davidlohr Bueso
2019-01-08 16:07     ` Roman Penyaev

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