| Message ID | 1451907925-15768-1-git-send-email-mst@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 04/01/16 11:46, Michael S. Tsirkin wrote: > drivers/xen/events/events_fifo.c uses rmb() to communicate with the > other side. > > For guests compiled with CONFIG_SMP, smp_rmb would be sufficient, so > rmb() here is only needed if a non-SMP guest runs on an SMP host. > > Switch to the virt_rmb barrier which serves this exact purpose. > > Pull in asm/barrier.h here to make sure the file is self-contained. Thanks! Acked-by: David Vrabel <david.vrabel@citrix.com> David
Hi Michael,
[auto build test ERROR on v4.4-rc8]
[also build test ERROR on next-20151231]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]
url: https://github.com/0day-ci/linux/commits/Michael-S-Tsirkin/xen-events-use-virt_xxx-barriers/20160104-194916
config: x86_64-randconfig-x008-01040711 (attached as .config)
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64
All errors (new ones prefixed by >>):
drivers/xen/events/events_fifo.c: In function 'consume_one_event':
>> drivers/xen/events/events_fifo.c:300:3: error: implicit declaration of function 'virt_rmb' [-Werror=implicit-function-declaration]
virt_rmb(); /* Ensure word is up-to-date before reading head. */
^
cc1: some warnings being treated as errors
vim +/virt_rmb +300 drivers/xen/events/events_fifo.c
294
295 /*
296 * Reached the tail last time? Read the new HEAD from the
297 * control block.
298 */
299 if (head == 0) {
> 300 virt_rmb(); /* Ensure word is up-to-date before reading head. */
301 head = control_block->head[priority];
302 }
303
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
diff --git a/drivers/xen/events/events_fifo.c b/drivers/xen/events/events_fifo.c index 96a1b8d..eff2b88 100644 --- a/drivers/xen/events/events_fifo.c +++ b/drivers/xen/events/events_fifo.c @@ -41,6 +41,7 @@ #include <linux/percpu.h> #include <linux/cpu.h> +#include <asm/barrier.h> #include <asm/sync_bitops.h> #include <asm/xen/hypercall.h> #include <asm/xen/hypervisor.h> @@ -296,7 +297,7 @@ static void consume_one_event(unsigned cpu, * control block. */ if (head == 0) { - rmb(); /* Ensure word is up-to-date before reading head. */ + virt_rmb(); /* Ensure word is up-to-date before reading head. */ head = control_block->head[priority]; }
drivers/xen/events/events_fifo.c uses rmb() to communicate with the other side. For guests compiled with CONFIG_SMP, smp_rmb would be sufficient, so rmb() here is only needed if a non-SMP guest runs on an SMP host. Switch to the virt_rmb barrier which serves this exact purpose. Pull in asm/barrier.h here to make sure the file is self-contained. Suggested-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- This is on top of my series: arch: barrier cleanup + barriers for virt and will be included in v3 of the series. drivers/xen/events/events_fifo.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)