Searched hist:"3 a5facd0" (Results 1 – 1 of 1) sorted by relevance
/openbmc/linux/arch/arm64/include/asm/ |
H A D | spinlock.h | 3a5facd0 Wed Jun 08 09:10:57 CDT 2016 Will Deacon <will.deacon@arm.com> arm64: spinlock: fix spin_unlock_wait for LSE atomics
Commit d86b8da04dfa ("arm64: spinlock: serialise spin_unlock_wait against concurrent lockers") fixed spin_unlock_wait for LL/SC-based atomics under the premise that the LSE atomics (in particular, the LDADDA instruction) are indivisible.
Unfortunately, these instructions are only indivisible when used with the -AL (full ordering) suffix and, consequently, the same issue can theoretically be observed with LSE atomics, where a later (in program order) load can be speculated before the write portion of the atomic operation.
This patch fixes the issue by performing a CAS of the lock once we've established that it's unlocked, in much the same way as the LL/SC code.
Fixes: d86b8da04dfa ("arm64: spinlock: serialise spin_unlock_wait against concurrent lockers") Signed-off-by: Will Deacon <will.deacon@arm.com> 3a5facd0 Wed Jun 08 09:10:57 CDT 2016 Will Deacon <will.deacon@arm.com> arm64: spinlock: fix spin_unlock_wait for LSE atomics Commit d86b8da04dfa ("arm64: spinlock: serialise spin_unlock_wait against concurrent lockers") fixed spin_unlock_wait for LL/SC-based atomics under the premise that the LSE atomics (in particular, the LDADDA instruction) are indivisible. Unfortunately, these instructions are only indivisible when used with the -AL (full ordering) suffix and, consequently, the same issue can theoretically be observed with LSE atomics, where a later (in program order) load can be speculated before the write portion of the atomic operation. This patch fixes the issue by performing a CAS of the lock once we've established that it's unlocked, in much the same way as the LL/SC code. Fixes: d86b8da04dfa ("arm64: spinlock: serialise spin_unlock_wait against concurrent lockers") Signed-off-by: Will Deacon <will.deacon@arm.com>
|