linux-kernel - [PATCH] HID: hidraw: fix nonblock read return EAGAIN after device removed

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Message-ID: <CAHLfQU=Hrufny=652k2mM7OcjxnRMH-kgj510FZrrKtiKNxdgw@mail.gmail.com>
Date:	Wed, 21 Nov 2012 15:20:31 +0800
From:	"founder.fang" <founder.fang@...il.com>
To:	jkosina@...e.cz
Cc:	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] HID: hidraw: fix nonblock read return EAGAIN after device removed

when nonblock read the condition check (file->f_flags & O_NONBLOCK)
always be true,
signal_pending and device exist checking never get a chance to run, so
the user mode code always
get EAGAIN even if device removed. move nonblock mode checking to the
last can fix this problem.

Signed-off-by: Founder Fang <founder.fang@...il.com>

--- hid-git/drivers/hid/hidraw.c.orig	2012-11-21 14:37:04.977106383 +0800
+++ hid-git/drivers/hid/hidraw.c	2012-11-21 14:40:35.882152200 +0800
@@ -57,10 +57,6 @@ static ssize_t hidraw_read(struct file *
 			set_current_state(TASK_INTERRUPTIBLE);

 			while (list->head == list->tail) {
-				if (file->f_flags & O_NONBLOCK) {
-					ret = -EAGAIN;
-					break;
-				}
 				if (signal_pending(current)) {
 					ret = -ERESTARTSYS;
 					break;
@@ -69,6 +65,10 @@ static ssize_t hidraw_read(struct file *
 					ret = -EIO;
 					break;
 				}
+				if (file->f_flags & O_NONBLOCK) {
+					ret = -EAGAIN;
+					break;
+				}

 				/* allow O_NONBLOCK to work well from other threads */
 				mutex_unlock(&list->read_mutex);
--
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