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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>
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1 changed files with 7 additions and 1 deletions
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@ -380,7 +380,7 @@ static void free_user_volumes(struct ubi_device *ubi)
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* @ubi: UBI device description object
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*
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* This function returns zero in case of success and a negative error code in
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* case of failure. Note, this function destroys all volumes if it failes.
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* case of failure. Note, this function destroys all volumes if it fails.
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*/
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static int uif_init(struct ubi_device *ubi)
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{
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@ -871,9 +871,15 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
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ubi->beb_rsvd_pebs);
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ubi_msg("max/mean erase counter: %d/%d", ubi->max_ec, ubi->mean_ec);
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/*
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* The below lock makes sure we do not race with 'ubi_thread()' which
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* checks @ubi->thread_enabled. Otherwise we may fail to wake it up.
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*/
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spin_lock(&ubi->wl_lock);
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if (!DBG_DISABLE_BGT)
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ubi->thread_enabled = 1;
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wake_up_process(ubi->bgt_thread);
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spin_unlock(&ubi->wl_lock);
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ubi_devices[ubi_num] = ubi;
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return ubi_num;
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