diff options
Diffstat (limited to 'drivers/hv/vmbus_drv.c')
| -rw-r--r-- | drivers/hv/vmbus_drv.c | 39 |
1 files changed, 28 insertions, 11 deletions
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 495337ec68f1..1f3e69d18d35 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -1101,8 +1101,9 @@ void vmbus_on_msg_dpc(unsigned long data) /* * The host can generate a rescind message while we * may still be handling the original offer. We deal with - * this condition by ensuring the processing is done on the - * same CPU. + * this condition by relying on the synchronization provided + * by offer_in_progress and by channel_mutex. See also the + * inline comments in vmbus_onoffer_rescind(). */ switch (hdr->msgtype) { case CHANNELMSG_RESCIND_CHANNELOFFER: @@ -1124,16 +1125,34 @@ void vmbus_on_msg_dpc(unsigned long data) * work queue: the RESCIND handler can not start to * run before the OFFER handler finishes. */ - schedule_work_on(VMBUS_CONNECT_CPU, - &ctx->work); + schedule_work(&ctx->work); break; case CHANNELMSG_OFFERCHANNEL: + /* + * The host sends the offer message of a given channel + * before sending the rescind message of the same + * channel. These messages are sent to the guest's + * connect CPU; the guest then starts processing them + * in the tasklet handler on this CPU: + * + * VMBUS_CONNECT_CPU + * + * [vmbus_on_msg_dpc()] + * atomic_inc() // CHANNELMSG_OFFERCHANNEL + * queue_work() + * ... + * [vmbus_on_msg_dpc()] + * schedule_work() // CHANNELMSG_RESCIND_CHANNELOFFER + * + * We rely on the memory-ordering properties of the + * queue_work() and schedule_work() primitives, which + * guarantee that the atomic increment will be visible + * to the CPUs which will execute the offer & rescind + * works by the time these works will start execution. + */ atomic_inc(&vmbus_connection.offer_in_progress); - queue_work_on(VMBUS_CONNECT_CPU, - vmbus_connection.work_queue, - &ctx->work); - break; + fallthrough; default: queue_work(vmbus_connection.work_queue, &ctx->work); @@ -1178,9 +1197,7 @@ static void vmbus_force_channel_rescinded(struct vmbus_channel *channel) INIT_WORK(&ctx->work, vmbus_onmessage_work); - queue_work_on(VMBUS_CONNECT_CPU, - vmbus_connection.work_queue, - &ctx->work); + queue_work(vmbus_connection.work_queue, &ctx->work); } #endif /* CONFIG_PM_SLEEP */ |