diff options
author | Fengguang Wu <fengguang.wu@intel.com> | 2013-10-16 16:47:03 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-10-17 00:35:53 -0400 |
commit | e3b6c655b91e01a1dade056cfa358581b47a5351 (patch) | |
tree | f2d77b6746591fa853bbb249ff65c7f2316929c1 /mm | |
parent | 5e9dd373dea43f61f5d3ce8b6667377a02c6fd42 (diff) |
writeback: fix negative bdi max pause
Toralf runs trinity on UML/i386. After some time it hangs and the last
message line is
BUG: soft lockup - CPU#0 stuck for 22s! [trinity-child0:1521]
It's found that pages_dirtied becomes very large. More than 1000000000
pages in this case:
period = HZ * pages_dirtied / task_ratelimit;
BUG_ON(pages_dirtied > 2000000000);
BUG_ON(pages_dirtied > 1000000000); <---------
UML debug printf shows that we got negative pause here:
ick: pause : -984
ick: pages_dirtied : 0
ick: task_ratelimit: 0
pause:
+ if (pause < 0) {
+ extern int printf(char *, ...);
+ printf("ick : pause : %li\n", pause);
+ printf("ick: pages_dirtied : %lu\n", pages_dirtied);
+ printf("ick: task_ratelimit: %lu\n", task_ratelimit);
+ BUG_ON(1);
+ }
trace_balance_dirty_pages(bdi,
Since pause is bounded by [min_pause, max_pause] where min_pause is also
bounded by max_pause. It's suspected and demonstrated that the
max_pause calculation goes wrong:
ick: pause : -717
ick: min_pause : -177
ick: max_pause : -717
ick: pages_dirtied : 14
ick: task_ratelimit: 0
The problem lies in the two "long = unsigned long" assignments in
bdi_max_pause() which might go negative if the highest bit is 1, and the
min_t(long, ...) check failed to protect it falling under 0. Fix all of
them by using "unsigned long" throughout the function.
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Reported-by: Toralf Förster <toralf.foerster@gmx.de>
Tested-by: Toralf Förster <toralf.foerster@gmx.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Richard Weinberger <richard@nod.at>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/page-writeback.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c index f5236f804aa6..63807583d8e8 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c | |||
@@ -1210,11 +1210,11 @@ static unsigned long dirty_poll_interval(unsigned long dirty, | |||
1210 | return 1; | 1210 | return 1; |
1211 | } | 1211 | } |
1212 | 1212 | ||
1213 | static long bdi_max_pause(struct backing_dev_info *bdi, | 1213 | static unsigned long bdi_max_pause(struct backing_dev_info *bdi, |
1214 | unsigned long bdi_dirty) | 1214 | unsigned long bdi_dirty) |
1215 | { | 1215 | { |
1216 | long bw = bdi->avg_write_bandwidth; | 1216 | unsigned long bw = bdi->avg_write_bandwidth; |
1217 | long t; | 1217 | unsigned long t; |
1218 | 1218 | ||
1219 | /* | 1219 | /* |
1220 | * Limit pause time for small memory systems. If sleeping for too long | 1220 | * Limit pause time for small memory systems. If sleeping for too long |
@@ -1226,7 +1226,7 @@ static long bdi_max_pause(struct backing_dev_info *bdi, | |||
1226 | t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8)); | 1226 | t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8)); |
1227 | t++; | 1227 | t++; |
1228 | 1228 | ||
1229 | return min_t(long, t, MAX_PAUSE); | 1229 | return min_t(unsigned long, t, MAX_PAUSE); |
1230 | } | 1230 | } |
1231 | 1231 | ||
1232 | static long bdi_min_pause(struct backing_dev_info *bdi, | 1232 | static long bdi_min_pause(struct backing_dev_info *bdi, |