mirror/openssl
2
0
Fork 0
mirror of https://github.com/openssl/openssl.git synced 2025-04-06 20:20:50 +08:00
Code Issues Packages Projects Releases Wiki Activity

Do some more cleanup in the RCU code

Browse Source 
Only a minimum of 2 qp's are necessary: one for the readers,
and at least one that writers can wait on for retirement.
There is no need for one additional qp that is always unused.
Also only one ACQUIRE barrier is necessary in get_hold_current_qp,
so the ATOMIC_LOAD of the reader_idx can be changed to RELAXED.
And finally clarify some comments.

Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/27012)
This commit is contained in:
Bernd Edlinger 2025-03-09 11:20:43 +01:00 committed by Tomas Mraz
parent 4a1a7fe5ce
commit a532f2302d
2 changed files with 10 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
crypto/threads_pthread.c
View File

@ -261,6 +261,8 @@ static struct rcu_qp *get_hold_current_qp(struct rcu_lock_st *lock)
/* get the current qp index */
for (;;) {
qp_idx = ATOMIC_LOAD_N(uint32_t, &lock->reader_idx, __ATOMIC_RELAXED);
/*
* Notes on use of __ATOMIC_ACQUIRE
* We need to ensure the following:
@ -271,10 +273,7 @@ static struct rcu_qp *get_hold_current_qp(struct rcu_lock_st *lock)
* of the lock is flushed from a local cpu cache so that we see any
* updates prior to the load. This is a non-issue on cache coherent
* systems like x86, but is relevant on other arches
* Note: This applies to the reload below as well
*/
qp_idx = ATOMIC_LOAD_N(uint32_t, &lock->reader_idx, __ATOMIC_ACQUIRE);
ATOMIC_ADD_FETCH(&lock->qp_group[qp_idx].users, (uint64_t)1,
__ATOMIC_ACQUIRE);
@ -475,6 +474,8 @@ void ossl_synchronize_rcu(CRYPTO_RCU_LOCK *lock)
* prior __ATOMIC_RELEASE write operation in ossl_rcu_read_unlock
* is visible prior to our read
* however this is likely just necessary to silence a tsan warning
* because the read side should not do any write operation
* outside the atomic itself
*/
do {
count = ATOMIC_LOAD_N(uint64_t, &qp->users, __ATOMIC_ACQUIRE);
@ -531,10 +532,10 @@ CRYPTO_RCU_LOCK *ossl_rcu_lock_new(int num_writers, OSSL_LIB_CTX *ctx)
struct rcu_lock_st *new;
/*
* We need a minimum of 3 qp's
* We need a minimum of 2 qp's
*/
if (num_writers < 3)
num_writers = 3;
if (num_writers < 2)
num_writers = 2;
ctx = ossl_lib_ctx_get_concrete(ctx);
if (ctx == NULL)
@ -550,8 +551,6 @@ CRYPTO_RCU_LOCK *ossl_rcu_lock_new(int num_writers, OSSL_LIB_CTX *ctx)
pthread_mutex_init(&new->alloc_lock, NULL);
pthread_cond_init(&new->prior_signal, NULL);
pthread_cond_init(&new->alloc_signal, NULL);
/* By default our first writer is already alloced */
new->writers_alloced = 1;
new->qp_group = allocate_new_qp_group(new, num_writers);
if (new->qp_group == NULL) {

8
crypto/threads_win.c
View File

@ -138,10 +138,10 @@ CRYPTO_RCU_LOCK *ossl_rcu_lock_new(int num_writers, OSSL_LIB_CTX *ctx)
struct rcu_lock_st *new;
/*
* We need a minimum of 3 qps
* We need a minimum of 2 qps
*/
if (num_writers < 3)
num_writers = 3;
if (num_writers < 2)
num_writers = 2;
ctx = ossl_lib_ctx_get_concrete(ctx);
if (ctx == NULL)
@ -160,8 +160,6 @@ CRYPTO_RCU_LOCK *ossl_rcu_lock_new(int num_writers, OSSL_LIB_CTX *ctx)
new->alloc_lock = ossl_crypto_mutex_new();
new->prior_lock = ossl_crypto_mutex_new();
new->qp_group = allocate_new_qp_group(new, num_writers);
/* By default the first qp is already alloced */
new->writers_alloced = 1;
if (new->qp_group == NULL
|| new->alloc_signal == NULL
|| new->prior_signal == NULL