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envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org 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. Reviewed-by: Richard Henderson Reviewed-by: David Hildenbrand Signed-off-by: Paolo Bonzini --- 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);