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| author | Peter Zijlstra <peterz@infradead.org> | 2024-09-09 12:50:09 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-10-17 15:21:29 +0200 |
| commit | 842d9156be5633e34c6a8811e81d36566b091280 (patch) | |
| tree | 94d2512bae9f7b25c1059e3c95b3fa072082c2f4 /drivers/virt | |
| parent | 0f05d6c3376bace13c1fd962fceadc5bbd233299 (diff) | |
| download | linux-842d9156be5633e34c6a8811e81d36566b091280.tar.gz linux-842d9156be5633e34c6a8811e81d36566b091280.tar.bz2 linux-842d9156be5633e34c6a8811e81d36566b091280.zip | |
jump_label: Fix static_key_slow_dec() yet again
[ Upstream commit 1d7f856c2ca449f04a22d876e36b464b7a9d28b6 ]
While commit 83ab38ef0a0b ("jump_label: Fix concurrency issues in
static_key_slow_dec()") fixed one problem, it created yet another,
notably the following is now possible:
slow_dec
if (try_dec) // dec_not_one-ish, false
// enabled == 1
slow_inc
if (inc_not_disabled) // inc_not_zero-ish
// enabled == 2
return
guard((mutex)(&jump_label_mutex);
if (atomic_cmpxchg(1,0)==1) // false, we're 2
slow_dec
if (try-dec) // dec_not_one, true
// enabled == 1
return
else
try_dec() // dec_not_one, false
WARN
Use dec_and_test instead of cmpxchg(), like it was prior to
83ab38ef0a0b. Add a few WARNs for the paranoid.
Fixes: 83ab38ef0a0b ("jump_label: Fix concurrency issues in static_key_slow_dec()")
Reported-by: "Darrick J. Wong" <djwong@kernel.org>
Tested-by: Klara Modin <klarasmodin@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers/virt')
0 files changed, 0 insertions, 0 deletions