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author | Rafael Aquini <aquini@redhat.com> | 2013-06-12 14:04:49 -0700 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-06-20 11:28:20 -0700 |
commit | 78ef884ebb6c02d45abefc95350f428be7390a26 (patch) | |
tree | 4b57c876160247db66c340770f66efeb3e05d7ca /include | |
parent | bac5719cdfb081dd68b0eeef7d9796c15fc29811 (diff) | |
download | kernel_samsung_smdk4412-78ef884ebb6c02d45abefc95350f428be7390a26.zip kernel_samsung_smdk4412-78ef884ebb6c02d45abefc95350f428be7390a26.tar.gz kernel_samsung_smdk4412-78ef884ebb6c02d45abefc95350f428be7390a26.tar.bz2 |
swap: avoid read_swap_cache_async() race to deadlock while waiting on discard I/O completion
commit cbab0e4eec299e9059199ebe6daf48730be46d2b upstream.
read_swap_cache_async() can race against get_swap_page(), and stumble
across a SWAP_HAS_CACHE entry in the swap map whose page wasn't brought
into the swapcache yet.
This transient swap_map state is expected to be transitory, but the
actual placement of discard at scan_swap_map() inserts a wait for I/O
completion thus making the thread at read_swap_cache_async() to loop
around its -EEXIST case, while the other end at get_swap_page() is
scheduled away at scan_swap_map(). This can leave the system deadlocked
if the I/O completion happens to be waiting on the CPU waitqueue where
read_swap_cache_async() is busy looping and !CONFIG_PREEMPT.
This patch introduces a cond_resched() call to make the aforementioned
read_swap_cache_async() busy loop condition to bail out when necessary,
thus avoiding the subtle race window.
Signed-off-by: Rafael Aquini <aquini@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Shaohua Li <shli@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
0 files changed, 0 insertions, 0 deletions