motorhead/qemu
1
0
Fork 0
mirror of https://github.com/Motorhead1991/qemu.git synced 2025-08-03 07:43:54 -06:00
Code Issues Projects Releases Packages Wiki Activity Actions

atomics: eliminate mb_read/mb_set

Browse source 
qatomic_mb_read and qatomic_mb_set were the very first atomic primitives
introduced for QEMU; their semantics are unclear and they provide a false
sense of safety.

The last use of qatomic_mb_read() has been removed, so delete it.
qatomic_mb_set() instead can survive as an optimized
qatomic_set()+smp_mb(), similar to Linux's smp_store_mb(), but
rename it to qatomic_set_mb() to match the order of the two
operations.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2023-03-03 14:37:51 +01:00
parent 09a49afeae
commit 06831001ac
11 changed files with 20 additions and 46 deletions
Download patch file Download diff file Expand all files Collapse all files

4
util/qemu-coroutine-lock.c
View file

@ -202,7 +202,7 @@ static void coroutine_fn qemu_co_mutex_lock_slowpath(AioContext *ctx,
push_waiter(mutex, &w);
/*
* Add waiter before reading mutex->handoff. Pairs with qatomic_mb_set
* Add waiter before reading mutex->handoff. Pairs with qatomic_set_mb
* in qemu_co_mutex_unlock.
*/
smp_mb__after_rmw();
@ -310,7 +310,7 @@ void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex)
our_handoff = mutex->sequence;
/* Set handoff before checking for waiters. */
qatomic_mb_set(&mutex->handoff, our_handoff);
qatomic_set_mb(&mutex->handoff, our_handoff);
if (!has_waiters(mutex)) {
/* The concurrent lock has not added itself yet, so it
* will be able to pick our handoff.