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authorDavid Rientjes <rientjes@google.com>2012-12-11 16:02:56 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-12-11 17:22:27 -0800
commite1e12d2f3104be886073ac6c5c4678f30b1b9e51 (patch)
treeb08cba1dba28e18cf7c2ffd8d076ce744e368b5f /mm/swapfile.c
parenta9c58b907dbc6821533dfc295b63caf111ff1f16 (diff)
downloadlinux-e1e12d2f3104be886073ac6c5c4678f30b1b9e51.tar.gz
mm, oom: fix race when specifying a thread as the oom origin
test_set_oom_score_adj() and compare_swap_oom_score_adj() are used to specify that current should be killed first if an oom condition occurs in between the two calls. The usage is short oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX); ... compare_swap_oom_score_adj(OOM_SCORE_ADJ_MAX, oom_score_adj); to store the thread's oom_score_adj, temporarily change it to the maximum score possible, and then restore the old value if it is still the same. This happens to still be racy, however, if the user writes OOM_SCORE_ADJ_MAX to /proc/pid/oom_score_adj in between the two calls. The compare_swap_oom_score_adj() will then incorrectly reset the old value prior to the write of OOM_SCORE_ADJ_MAX. To fix this, introduce a new oom_flags_t member in struct signal_struct that will be used for per-thread oom killer flags. KSM and swapoff can now use a bit in this member to specify that threads should be killed first in oom conditions without playing around with oom_score_adj. This also allows the correct oom_score_adj to always be shown when reading /proc/pid/oom_score. Signed-off-by: David Rientjes <rientjes@google.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: Michal Hocko <mhocko@suse.cz> Cc: Anton Vorontsov <anton.vorontsov@linaro.org> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swapfile.c')
-rw-r--r--mm/swapfile.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index bb6f6a04e92..e97a0e5aea9 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1498,7 +1498,6 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
struct address_space *mapping;
struct inode *inode;
struct filename *pathname;
- short oom_score_adj;
int i, type, prev;
int err;
@@ -1557,9 +1556,9 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
p->flags &= ~SWP_WRITEOK;
spin_unlock(&swap_lock);
- oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX);
+ set_current_oom_origin();
err = try_to_unuse(type, false, 0); /* force all pages to be unused */
- compare_swap_oom_score_adj(OOM_SCORE_ADJ_MAX, oom_score_adj);
+ clear_current_oom_origin();
if (err) {
/* re-insert swap space back into swap_list */