diff options
| author | Dexuan Cui <decui@microsoft.com> | 2015-01-14 10:55:10 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-01-25 18:17:58 +0100 |
| commit | d9b1652947c695d247b5e4603a16213ec55661ed (patch) | |
| tree | d9d5b81e2b05aeadc3eebda0dac8f20859e89097 | |
| parent | Drivers: hv: vmbus: Support a vmbus API for efficiently sending page arrays (diff) | |
| download | linux-d9b1652947c695d247b5e4603a16213ec55661ed.tar.xz linux-d9b1652947c695d247b5e4603a16213ec55661ed.zip | |
hv: hv_fcopy: drop the obsolete message on transfer failure
In the case the user-space daemon crashes, hangs or is killed, we
need to down the semaphore, otherwise, after the daemon starts next
time, the obsolete data in fcopy_transaction.message or
fcopy_transaction.fcopy_msg will be used immediately.
Cc: Jason Wang <jasowang@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to '')
| -rw-r--r-- | drivers/hv/hv_fcopy.c | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/drivers/hv/hv_fcopy.c b/drivers/hv/hv_fcopy.c index 23b2ce294c4c..cd453e4b2a07 100644 --- a/drivers/hv/hv_fcopy.c +++ b/drivers/hv/hv_fcopy.c @@ -86,6 +86,18 @@ static void fcopy_work_func(struct work_struct *dummy) * process the pending transaction. */ fcopy_respond_to_host(HV_E_FAIL); + + /* In the case the user-space daemon crashes, hangs or is killed, we + * need to down the semaphore, otherwise, after the daemon starts next + * time, the obsolete data in fcopy_transaction.message or + * fcopy_transaction.fcopy_msg will be used immediately. + * + * NOTE: fcopy_read() happens to get the semaphore (very rare)? We're + * still OK, because we've reported the failure to the host. + */ + if (down_trylock(&fcopy_transaction.read_sema)) + ; + } static int fcopy_handle_handshake(u32 version) @@ -344,6 +356,14 @@ static int fcopy_open(struct inode *inode, struct file *f) return 0; } +/* XXX: there are still some tricky corner cases, e.g., + * 1) In a SMP guest, when fcopy_release() runs between + * schedule_delayed_work() and fcopy_send_data(), there is + * still a chance an obsolete message will be queued. + * + * 2) When the fcopy daemon is running, if we unload the driver, + * we'll notice a kernel oops when we kill the daemon later. + */ static int fcopy_release(struct inode *inode, struct file *f) { /* @@ -351,6 +371,13 @@ static int fcopy_release(struct inode *inode, struct file *f) */ in_hand_shake = true; opened = false; + + if (cancel_delayed_work_sync(&fcopy_work)) { + /* We haven't up()-ed the semaphore(very rare)? */ + if (down_trylock(&fcopy_transaction.read_sema)) + ; + fcopy_respond_to_host(HV_E_FAIL); + } return 0; } |