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

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Date:	Mon, 26 Nov 2012 10:30:37 +0800
From:	"founder.fang" <founder.fang@...il.com>
To:	dmitry.torokhov@...il.com, jkosina@...e.cz,
	linux-input@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] HID: hidraw: fix nonblock read return EAGAIN after device removed

Hi Linux-Input, Jiri, Dmitry,
this patch is related to nonblock read on hidraw device.
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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