xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

RAID5: revert e9e4c377e2 to fix a livelock

Browse Source 
Revert commit
e9e4c377e2f563(md/raid5: per hash value and exclusive wait_for_stripe)

The problem is raid5_get_active_stripe waits on
conf->wait_for_stripe[hash]. Assume hash is 0. My test release stripes
in this order:
- release all stripes with hash 0
- raid5_get_active_stripe still sleeps since active_stripes >
  max_nr_stripes * 3 / 4
- release all stripes with hash other than 0. active_stripes becomes 0
- raid5_get_active_stripe still sleeps, since nobody wakes up
  wait_for_stripe[0]
The system live locks. The problem is active_stripes isn't a per-hash
count. Revert the patch makes the live lock go away.

Cc: stable@vger.kernel.org (v4.2+)
Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: NeilBrown <neilb@suse.de>
Signed-off-by: Shaohua Li <shli@fb.com>
This commit is contained in:
Shaohua Li
2016-02-25 16:24:42 -08:00
parent 27a353c026
commit 6ab2a4b806
2 changed files with 9 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/md/raid5.h
View File

@@ -524,7 +524,7 @@ struct r5conf {
atomic_t empty_inactive_list_nr;
struct llist_head released_stripes;
wait_queue_head_t wait_for_quiescent;
wait_queue_head_t wait_for_stripe[NR_STRIPE_HASH_LOCKS];
wait_queue_head_t wait_for_stripe;
wait_queue_head_t wait_for_overlap;
unsigned long cache_state;
#define R5_INACTIVE_BLOCKED 1 /* release of inactive stripes blocked,