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authorFengguang Wu <fengguang.wu@intel.com>2013-10-16 13:47:03 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-10-16 21:35:53 -0700
commite3b6c655b91e01a1dade056cfa358581b47a5351 (patch)
treef2d77b6746591fa853bbb249ff65c7f2316929c1 /mm
parent5e9dd373dea43f61f5d3ce8b6667377a02c6fd42 (diff)
downloadlinaro-lsk-e3b6c655b91e01a1dade056cfa358581b47a5351.tar.gz
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.c10
1 files changed, 5 insertions, 5 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index f5236f804aa..63807583d8e 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1210,11 +1210,11 @@ static unsigned long dirty_poll_interval(unsigned long dirty,
return 1;
}
-static long bdi_max_pause(struct backing_dev_info *bdi,
- unsigned long bdi_dirty)
+static unsigned long bdi_max_pause(struct backing_dev_info *bdi,
+ unsigned long bdi_dirty)
{
- long bw = bdi->avg_write_bandwidth;
- long t;
+ unsigned long bw = bdi->avg_write_bandwidth;
+ unsigned long t;
/*
* 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,
t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8));
t++;
- return min_t(long, t, MAX_PAUSE);
+ return min_t(unsigned long, t, MAX_PAUSE);
}
static long bdi_min_pause(struct backing_dev_info *bdi,