[lustre-devel] [PATCH 022/622] lustre: llite: yield cpu after call to ll_agl_trigger

[James Simmons]

From: Ann Koehler <amk at cray.com>

The statahead and agl threads loop over all entries in the
directory without yielding the CPU. If the number of entries in
the directory is large enough then these threads may trigger
soft lockups. The fix is to add calls to cond_resched() after
calling ll_agl_trigger(), which gets the glimpse lock for a
file.

Cray-bug-id: LUS-2584
WC-bug-id: https://jira.whamcloud.com/browse/LU-10649
Lustre-commit: 031001f0d438 ("LU-10649 llite: yield cpu after call to ll_agl_trigger")
Signed-off-by: Ann Koehler <amk at cray.com>
Signed-off-by: Chris Horn <hornc at cray.com>
Reviewed-on: https://review.whamcloud.com/31240
Reviewed-by: Patrick Farrell <pfarrell at whamcloud.com>
Reviewed-by: Sergey Cheremencev <c17829 at cray.com>
Reviewed-by: Oleg Drokin <green at whamcloud.com>
Signed-off-by: James Simmons <jsimmons at infradead.org>
---
 fs/lustre/llite/statahead.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/lustre/llite/statahead.c b/fs/lustre/llite/statahead.c
index 99b3fee..4a61dac 100644
--- a/fs/lustre/llite/statahead.c
+++ b/fs/lustre/llite/statahead.c
@@ -907,6 +907,7 @@ static int ll_agl_thread(void *arg)
 			list_del_init(&clli->lli_agl_list);
 			spin_unlock(&plli->lli_agl_lock);
 			ll_agl_trigger(&clli->lli_vfs_inode, sai);
+			cond_resched();
 		} else {
 			spin_unlock(&plli->lli_agl_lock);
 		}
@@ -1071,7 +1072,7 @@ static int ll_statahead_thread(void *arg)
 
 					ll_agl_trigger(&clli->lli_vfs_inode,
 						       sai);
-
+					cond_resched();
 					spin_lock(&lli->lli_agl_lock);
 				}
 				spin_unlock(&lli->lli_agl_lock);
-- 
1.8.3.1