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SubjectRE: [PATCH] Drivers: hv: hv_fcopy: fix a race condition for SMP guest
Date


> -----Original Message-----
> From: Dexuan Cui [mailto:decui@microsoft.com]
> Sent: Wednesday, July 16, 2014 12:01 AM
> To: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org; driverdev-
> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> jasowang@redhat.com
> Cc: KY Srinivasan; Haiyang Zhang
> Subject: [PATCH] Drivers: hv: hv_fcopy: fix a race condition for SMP guest
>
> 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 <lizzha@microsoft.com> for the initial investigation on the
> bug.
>
> This addresses https://bugzilla.redhat.com/show_bug.cgi?id=1118123
>
> Tested-by: Liz Zhang <lizzha@microsoft.com>
> Cc: K. Y. Srinivasan <kys@microsoft.com>
> Cc: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Dexuan Cui <decui@microsoft.com>

Thanks Dexuan.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>


K. Y

> ---
> drivers/hv/hv_fcopy.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> 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;
> --
> 1.9.1



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