Drivers: hv: hv_fcopy: fix a race condition for SMP guest

2ef82d24 · Dexuan Cui <[email protected]> · 2014-07-16 00:00:45 -07:00

We should schedule the 5s "timer work" before starting the data transfer,
otherwise, the data transfer code may finish so fast on another
virtual cpu that when the code(fcopy_write()) trying to cancel the 5s
"timer work" can occasionally fail because the "timer work" may haven't
been scheduled yet and as a result the fcopy process will be aborted
wrongly by fcopy_work_func() in 5s.

Thank Liz Zhang <[email protected]> for the initial investigation
on the bug.

This addresses https://bugzilla.redhat.com/show_bug.cgi?id=1118123

Tested-by: Liz Zhang <[email protected]>
Cc: Haiyang Zhang <[email protected]>
Cc: [email protected]
Signed-off-by: Dexuan Cui <[email protected]>
Signed-off-by: K. Y. Srinivasan <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Commit: 2ef82d24f445e82f80e235f44eb9d1bc933e3670
Parents: 1795cd9b

Changes

1 files changed · +1 −1

File	Status	Add	Del	Content
drivers/hv/hv_fcopy.c	modified	+1	−1	View file

drivers/hv/hv_fcopy.c

View file

diff --git a/drivers/hv/hv_fcopy.c b/drivers/hv/hv_fcopy.c
index eaaa3d8..23b2ce2 100644
--- a/drivers/hv/hv_fcopy.c
+++ b/drivers/hv/hv_fcopy.c
@@ -246,8 +246,8 @@ void hv_fcopy_onchannelcallback(void *context)
 		/*
 		 * Send the information to the user-level daemon.
 		 */
-		fcopy_send_data();
 		schedule_delayed_work(&fcopy_work, 5*HZ);
+		fcopy_send_data();
 		return;
 	}
 	icmsghdr->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;