diff options
| author |   Damjan Marion <damarion@cisco.com> | 2020-04-21 20:14:34 +0200 |
|---|---|---|
| committer |   Damjan Marion <dmarion@me.com> | 2020-04-22 08:47:29 +0000 |
| commit | 74ee18b0b33aad974705ae16739a86c48f3b966b (patch) | |
| tree | 2b911b913d5052163b04410c3716b711aaacf456 | |
| parent | 801ec2a080d9414b3fab80906333bdb94b5d4043 (diff) | |
vppinfra: fix potential race in bihash bucket lock
Type: improvement
Change-Id: Ia04bd26ecd689894753e036e52920316de611910
Signed-off-by: Damjan Marion <damarion@cisco.com>
| -rw-r--r-- | src/vppinfra/bihash_template.h | 20 |
1 files changed, 9 insertions, 11 deletions
diff --git a/src/vppinfra/bihash_template.h b/src/vppinfra/bihash_template.h index b8e0a239013..50b4af65710 100644 --- a/src/vppinfra/bihash_template.h +++ b/src/vppinfra/bihash_template.h @@ -260,21 +260,19 @@ static inline void BV (clib_bihash_alloc_unlock) (BVT (clib_bihash) * h) static inline void BV (clib_bihash_lock_bucket) (BVT (clib_bihash_bucket) * b) { - BVT (clib_bihash_bucket) unlocked_bucket, locked_bucket; + /* *INDENT-OFF* */ + BVT (clib_bihash_bucket) mask = { .lock = 1 }; + /* *INDENT-ON* */ + u64 old; - locked_bucket.as_u64 = unlocked_bucket.as_u64 = b->as_u64; - unlocked_bucket.lock = 0; - locked_bucket.lock = 1; +try_again: + old = clib_atomic_fetch_or (&b->as_u64, mask.as_u64); - while (__atomic_compare_exchange_n (&b->as_u64, &unlocked_bucket.as_u64, - locked_bucket.as_u64, 1 /* weak */ , - __ATOMIC_ACQUIRE, - __ATOMIC_ACQUIRE) == 0) + if (PREDICT_FALSE (old & mask.as_u64)) { + /* somebody else flipped the bit, try again */ CLIB_PAUSE (); - locked_bucket.as_u64 = unlocked_bucket.as_u64 = b->as_u64; - unlocked_bucket.lock = 0; - locked_bucket.lock = 1; + goto try_again; } } |