diff options
Diffstat (limited to 'drivers/hv/hv_fcopy.c')
| -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; } |