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authorArtem Bityutskiy <Artem.Bityutskiy@nokia.com>2009-05-23 13:44:09 +0300
committerArtem Bityutskiy <Artem.Bityutskiy@nokia.com>2009-05-26 12:47:47 +0300
commitddbd3b61708483f73dbcc62a94d16cc7db928cba (patch)
tree7600caa289d1517e8642d6be21d0a0cfe88c40d5
parent95c9c1da79e59fd10ec5da3aeba22981383f7040 (diff)
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UBI: fix race condition
This patch fixes a minor problem where we may fail to wake upe the UBI background thread. This is not fatal at all, it may just result at sligtly worse performace for a short period of time, just because the thread will be woken up when real I/O on the UBI starts. Anywey, the issue is the race condition between 'ubi_attach_mtd_dev()' and 'ubi_thread()'. If we do not serialize them, the 'wake_up_process()' call may be done before 'ubi_thread()' went seep, but after it checked 'ubi->thread_enabled'. This issue was spotted by Shin Hong <hongshin@gmail.com> Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
-rw-r--r--drivers/mtd/ubi/build.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 2c3269e..1405b55 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -380,7 +380,7 @@ static void free_user_volumes(struct ubi_device *ubi)
* @ubi: UBI device description object
*
* This function returns zero in case of success and a negative error code in
- * case of failure. Note, this function destroys all volumes if it failes.
+ * case of failure. Note, this function destroys all volumes if it fails.
*/
static int uif_init(struct ubi_device *ubi)
{
@@ -871,9 +871,15 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
ubi->beb_rsvd_pebs);
ubi_msg("max/mean erase counter: %d/%d", ubi->max_ec, ubi->mean_ec);
+ /*
+ * The below lock makes sure we do not race with 'ubi_thread()' which
+ * checks @ubi->thread_enabled. Otherwise we may fail to wake it up.
+ */
+ spin_lock(&ubi->wl_lock);
if (!DBG_DISABLE_BGT)
ubi->thread_enabled = 1;
wake_up_process(ubi->bgt_thread);
+ spin_unlock(&ubi->wl_lock);
ubi_devices[ubi_num] = ubi;
return ubi_num;