[lkml]   [2018]   [Oct]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH AUTOSEL 3.18 54/98] nfs: fix high load average due to callback thread sleeping
From: Jeff Layton <>

[ Upstream commit 5d05e54af3cdbb13cf19c557ff2184781b91a22c ]

Chuck pointed out a problem that crept in with commit 6ffa30d3f734 (nfs:
don't call blocking operations while !TASK_RUNNING). Linux counts tasks
in uninterruptible sleep against the load average, so this caused the
system's load average to be pinned at at least 1 when there was a
NFSv4.1+ mount active.

Not a huge problem, but it's probably worth fixing before we get too
many complaints about it. This patch converts the code back to use
TASK_INTERRUPTIBLE sleep, simply has it flush any signals on each loop
iteration. In practice no one should really be signalling this thread at
all, so I think this is reasonably safe.

With this change, there's also no need to game the hung task watchdog so
we can also convert the schedule_timeout call back to a normal schedule.

Cc: <>
Reported-by: Chuck Lever <>
Signed-off-by: Jeff Layton <>
Tested-by: Chuck Lever <>
Fixes: commit 6ffa30d3f734 (“nfs: don't call blocking . . .”)
Signed-off-by: Trond Myklebust <>
Signed-off-by: Sasha Levin <>
fs/nfs/callback.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c
index 3b8cdb8298c4..a78558a25035 100644
--- a/fs/nfs/callback.c
+++ b/fs/nfs/callback.c
@@ -128,7 +128,7 @@ nfs41_callback_svc(void *vrqstp)
if (try_to_freeze())

- prepare_to_wait(&serv->sv_cb_waitq, &wq, TASK_UNINTERRUPTIBLE);
+ prepare_to_wait(&serv->sv_cb_waitq, &wq, TASK_INTERRUPTIBLE);
if (!list_empty(&serv->sv_cb_list)) {
req = list_first_entry(&serv->sv_cb_list,
@@ -142,10 +142,10 @@ nfs41_callback_svc(void *vrqstp)
} else {
- /* schedule_timeout to game the hung task watchdog */
- schedule_timeout(60 * HZ);
+ schedule();
finish_wait(&serv->sv_cb_waitq, &wq);
+ flush_signals(current);
return 0;
 \ /
  Last update: 2018-10-25 16:26    [W:0.297 / U:8.828 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site