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atomics: eliminate mb_read/mb_set

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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
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4
accel/tcg/tcg-accel-ops-rr.c
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@ -244,7 +244,7 @@ static void *rr_cpu_thread_fn(void *arg)
while (cpu && cpu_work_list_empty(cpu) && !cpu->exit_request) {
/* Store rr_current_cpu before evaluating cpu_can_run(). */
qatomic_mb_set(&rr_current_cpu, cpu);
qatomic_set_mb(&rr_current_cpu, cpu);
current_cpu = cpu;
@ -287,7 +287,7 @@ static void *rr_cpu_thread_fn(void *arg)
qatomic_set(&rr_current_cpu, NULL);
if (cpu && cpu->exit_request) {
qatomic_mb_set(&cpu->exit_request, 0);
qatomic_set_mb(&cpu->exit_request, 0);
}
if (icount_enabled() && all_cpu_threads_idle()) {