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author | David S. Miller <davem@davemloft.net> | 2015-02-18 02:48:51 (GMT) |
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committer | David S. Miller <davem@davemloft.net> | 2015-02-18 02:48:51 (GMT) |
commit | fece13ca005a5f559147e9424321f4b5e01272b4 (patch) | |
tree | 54e762e70afb664d14152e6bcf89a48be3fb9c13 /drivers/hv/hv_fcopy.c | |
parent | 855e7e7174bade3f2b63077a81eea5aab525dbf6 (diff) | |
parent | f5af19d10d151c5a2afae3306578f485c244db25 (diff) | |
download | linux-fece13ca005a5f559147e9424321f4b5e01272b4.tar.xz |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
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 23b2ce2..cd453e4 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; } |