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From:   Roman Penyaev <rpenyaev@suse.de>
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 2/3] epoll: loosen irq safety in ep_poll_callback()
Date:   Wed, 12 Dec 2018 12:03:56 +0100
Message-Id: <20181212110357.25656-3-rpenyaev@suse.de>
In-Reply-To: <20181212110357.25656-1-rpenyaev@suse.de>
References: <20181212110357.25656-1-rpenyaev@suse.de>
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Callers of the ep_poll_callback() (all set of wake_up_*poll()) disable
interrupts, so no need to save/restore irq flags.

Signed-off-by: Roman Penyaev <rpenyaev@suse.de>
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 | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 3627c2e07149..ea0025e77519 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1124,13 +1124,15 @@ struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd,
 static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
 {
 	int pwake = 0;
-	unsigned long flags;
 	struct epitem *epi = ep_item_from_wait(wait);
 	struct eventpoll *ep = epi->ep;
 	__poll_t pollflags = key_to_poll(key);
 	int ewake = 0;
 
-	spin_lock_irqsave(&ep->wq.lock, flags);
+	/* Interrupts are disabled by the wake_up_*poll() callers */
+	lockdep_assert_irqs_disabled();
+
+	spin_lock(&ep->wq.lock);
 
 	ep_set_busy_poll_napi_id(epi);
 
@@ -1207,7 +1209,7 @@ static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, v
 		pwake++;
 
 out_unlock:
-	spin_unlock_irqrestore(&ep->wq.lock, flags);
+	spin_unlock(&ep->wq.lock);
 
 	/* We have to call this outside the lock */
 	if (pwake)
-- 
2.19.1