diff options
Diffstat (limited to 'drivers/hv/hyperv_vmbus.h')
| -rw-r--r-- | drivers/hv/hyperv_vmbus.h | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h index e5203e4d6782..718b5c72f0c8 100644 --- a/drivers/hv/hyperv_vmbus.h +++ b/drivers/hv/hyperv_vmbus.h @@ -625,9 +625,21 @@ extern struct vmbus_channel_message_table_entry channel_message_table[CHANNELMSG_COUNT]; /* Free the message slot and signal end-of-message if required */ -static inline void vmbus_signal_eom(struct hv_message *msg) +static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type) { - msg->header.message_type = HVMSG_NONE; + /* + * On crash we're reading some other CPU's message page and we need + * to be careful: this other CPU may already had cleared the header + * and the host may already had delivered some other message there. + * In case we blindly write msg->header.message_type we're going + * to lose it. We can still lose a message of the same type but + * we count on the fact that there can only be one + * CHANNELMSG_UNLOAD_RESPONSE and we don't care about other messages + * on crash. + */ + if (cmpxchg(&msg->header.message_type, old_msg_type, + HVMSG_NONE) != old_msg_type) + return; /* * Make sure the write to MessageType (ie set to |