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[PATCH 4/8] edu: add smp_mb__after_rmw()
From: |
Paolo Bonzini |
Subject: |
[PATCH 4/8] edu: add smp_mb__after_rmw() |
Date: |
Fri, 3 Mar 2023 18:19:35 +0100 |
Ensure ordering between clearing the COMPUTING flag and checking
IRQFACT, and between setting the IRQFACT flag and checking
COMPUTING. This ensures that no wakeups are lost.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
hw/misc/edu.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/hw/misc/edu.c b/hw/misc/edu.c
index e935c418d400..a1f8bc77e770 100644
--- a/hw/misc/edu.c
+++ b/hw/misc/edu.c
@@ -267,6 +267,8 @@ static void edu_mmio_write(void *opaque, hwaddr addr,
uint64_t val,
case 0x20:
if (val & EDU_STATUS_IRQFACT) {
qatomic_or(&edu->status, EDU_STATUS_IRQFACT);
+ /* Order check of the COMPUTING flag after setting IRQFACT. */
+ smp_mb__after_rmw();
} else {
qatomic_and(&edu->status, ~EDU_STATUS_IRQFACT);
}
@@ -349,6 +351,9 @@ static void *edu_fact_thread(void *opaque)
qemu_mutex_unlock(&edu->thr_mutex);
qatomic_and(&edu->status, ~EDU_STATUS_COMPUTING);
+ /* Clear COMPUTING flag before checking IRQFACT. */
+ smp_mb__after_rmw();
+
if (qatomic_read(&edu->status) & EDU_STATUS_IRQFACT) {
qemu_mutex_lock_iothread();
edu_raise_irq(edu, FACT_IRQ);
--
2.39.1
- Re: [PATCH 1/8] qatomic: add smp_mb__before/after_rmw(), (continued)
- [PATCH 2/8] qemu-thread-posix: cleanup, fix, document QemuEvent, Paolo Bonzini, 2023/03/03
- [PATCH 3/8] qemu-thread-win32: cleanup, fix, document QemuEvent, Paolo Bonzini, 2023/03/03
- Re: [PATCH 3/8] qemu-thread-win32: cleanup, fix, document QemuEvent, Richard Henderson, 2023/03/05
- Re: [PATCH 3/8] qemu-thread-win32: cleanup, fix, document QemuEvent, David Hildenbrand, 2023/03/06
- Re: [PATCH 3/8] qemu-thread-win32: cleanup, fix, document QemuEvent, Paolo Bonzini, 2023/03/06
- Re: [PATCH 3/8] qemu-thread-win32: cleanup, fix, document QemuEvent, David Hildenbrand, 2023/03/06
- Re: [PATCH 3/8] qemu-thread-win32: cleanup, fix, document QemuEvent, Paolo Bonzini, 2023/03/06
[PATCH 4/8] edu: add smp_mb__after_rmw(),
Paolo Bonzini <=
[PATCH 5/8] util/async: add smp_mb__after_rmw() around BH enqueue/dequeue, Paolo Bonzini, 2023/03/03