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tb-maint: do not use mb_read/mb_set 

The load side can use a relaxed load, which will surely happen before
the work item is run by async_safe_run_on_cpu() or before double-checking
under mmap_lock.  The store side can use an atomic RMW operation.

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 13:12:50 +01:00
parent 8f593ba9c5
commit 20f46806b3
1 changed files with 2 additions and 2 deletions
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4
accel/tcg/tb-maint.c
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@ -746,7 +746,7 @@ static void do_tb_flush(CPUState *cpu, run_on_cpu_data tb_flush_count)
tcg_region_reset_all(); tcg_region_reset_all();
/* XXX: flush processor icache at this point if cache flush is expensive */ /* XXX: flush processor icache at this point if cache flush is expensive */
qatomic_mb_set(&tb_ctx.tb_flush_count, tb_ctx.tb_flush_count + 1); qatomic_inc(&tb_ctx.tb_flush_count);
done: done:
mmap_unlock(); mmap_unlock();
@ -758,7 +758,7 @@ done:
void tb_flush(CPUState *cpu) void tb_flush(CPUState *cpu)
{ {
if (tcg_enabled()) { if (tcg_enabled()) {
unsigned tb_flush_count = qatomic_mb_read(&tb_ctx.tb_flush_count); unsigned tb_flush_count = qatomic_read(&tb_ctx.tb_flush_count);
if (cpu_in_exclusive_context(cpu)) { if (cpu_in_exclusive_context(cpu)) {
do_tb_flush(cpu, RUN_ON_CPU_HOST_INT(tb_flush_count)); do_tb_flush(cpu, RUN_ON_CPU_HOST_INT(tb_flush_count));