From dad72a1d28442b03aac86836a42de2d00a1014ab Mon Sep 17 00:00:00 2001 From: Dexuan Cui Date: Sat, 4 Mar 2017 18:13:58 -0700 Subject: [PATCH] vmbus: remove hv_event_tasklet_disable/enable With the recent introduction of per-channel tasklet, we need to update the way we handle the 3 concurrency issues: 1. hv_process_channel_removal -> percpu_channel_deq vs. vmbus_chan_sched -> list_for_each_entry(..., percpu_list); 2. vmbus_process_offer -> percpu_channel_enq/deq vs. vmbus_chan_sched. 3. vmbus_close_internal vs. the per-channel tasklet vmbus_on_event; The first 2 issues can be handled by Stephen's recent patch "vmbus: use rcu for per-cpu channel list", and the third issue can be handled by calling tasklet_disable in vmbus_close_internal here. We don't need the original hv_event_tasklet_disable/enable since we now use per-channel tasklet instead of the previous per-CPU tasklet, and actually we must remove them due to the side effect now: vmbus_process_offer -> hv_event_tasklet_enable -> tasklet_schedule will start the per-channel callback prematurely, cauing NULL dereferencing (the channel may haven't been properly configured to run the callback yet). Fixes: 631e63a9f346 ("vmbus: change to per channel tasklet") Signed-off-by: Dexuan Cui Cc: "K. Y. Srinivasan" Cc: Haiyang Zhang Cc: Stephen Hemminger Tested-by: Vitaly Kuznetsov Signed-off-by: K. Y. Srinivasan Signed-off-by: Greg Kroah-Hartman --- drivers/hv/channel.c | 12 ++++-------- drivers/hv/channel_mgmt.c | 19 ------------------- include/linux/hyperv.h | 3 --- 3 files changed, 4 insertions(+), 30 deletions(-) diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c index bd0d1988feb2..57b2958205c7 100644 --- a/drivers/hv/channel.c +++ b/drivers/hv/channel.c @@ -530,15 +530,13 @@ static int vmbus_close_internal(struct vmbus_channel *channel) int ret; /* - * vmbus_on_event(), running in the tasklet, can race + * vmbus_on_event(), running in the per-channel tasklet, can race * with vmbus_close_internal() in the case of SMP guest, e.g., when * the former is accessing channel->inbound.ring_buffer, the latter - * could be freeing the ring_buffer pages. - * - * To resolve the race, we can serialize them by disabling the - * tasklet when the latter is running here. + * could be freeing the ring_buffer pages, so here we must stop it + * first. */ - hv_event_tasklet_disable(channel); + tasklet_disable(&channel->callback_event); /* * In case a device driver's probe() fails (e.g., @@ -605,8 +603,6 @@ static int vmbus_close_internal(struct vmbus_channel *channel) get_order(channel->ringbuffer_pagecount * PAGE_SIZE)); out: - hv_event_tasklet_enable(channel); - return ret; } diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c index d2cfa3eb71a2..bf846d078d85 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -382,19 +382,6 @@ static void vmbus_release_relid(u32 relid) true); } -void hv_event_tasklet_disable(struct vmbus_channel *channel) -{ - tasklet_disable(&channel->callback_event); -} - -void hv_event_tasklet_enable(struct vmbus_channel *channel) -{ - tasklet_enable(&channel->callback_event); - - /* In case there is any pending event */ - tasklet_schedule(&channel->callback_event); -} - void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid) { unsigned long flags; @@ -403,7 +390,6 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid) BUG_ON(!channel->rescind); BUG_ON(!mutex_is_locked(&vmbus_connection.channel_mutex)); - hv_event_tasklet_disable(channel); if (channel->target_cpu != get_cpu()) { put_cpu(); smp_call_function_single(channel->target_cpu, @@ -412,7 +398,6 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid) percpu_channel_deq(channel); put_cpu(); } - hv_event_tasklet_enable(channel); if (channel->primary_channel == NULL) { list_del(&channel->listentry); @@ -506,7 +491,6 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) init_vp_index(newchannel, dev_type); - hv_event_tasklet_disable(newchannel); if (newchannel->target_cpu != get_cpu()) { put_cpu(); smp_call_function_single(newchannel->target_cpu, @@ -516,7 +500,6 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) percpu_channel_enq(newchannel); put_cpu(); } - hv_event_tasklet_enable(newchannel); /* * This state is used to indicate a successful open @@ -566,7 +549,6 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) list_del(&newchannel->listentry); mutex_unlock(&vmbus_connection.channel_mutex); - hv_event_tasklet_disable(newchannel); if (newchannel->target_cpu != get_cpu()) { put_cpu(); smp_call_function_single(newchannel->target_cpu, @@ -575,7 +557,6 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) percpu_channel_deq(newchannel); put_cpu(); } - hv_event_tasklet_enable(newchannel); vmbus_release_relid(newchannel->offermsg.child_relid); diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index c4c7ae91f9d1..970771a5f739 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -1437,9 +1437,6 @@ extern bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp, u8 *buf, const int *srv_version, int srv_vercnt, int *nego_fw_version, int *nego_srv_version); -void hv_event_tasklet_disable(struct vmbus_channel *channel); -void hv_event_tasklet_enable(struct vmbus_channel *channel); - void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid); void vmbus_setevent(struct vmbus_channel *channel);