lkml.org 
[lkml]   [2014]   [Nov]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH v2] ACPI/osl: speedup grace period in acpi_os_map_cleanup
Date
On Sunday, November 09, 2014 02:00:38 PM Paul E. McKenney wrote:
> On Sun, Nov 09, 2014 at 01:53:37PM +0400, Konstantin Khlebnikov wrote:
> > ACPI maintains cache of ioremap regions to speed up operations and
> > access to them from irq context where ioremap() calls aren't allowed.
> > This code abuses synchronize_rcu() on unmap path for synchronization
> > with fast-path in acpi_os_read/write_memory which uses this cache.
> >
> > Since v3.10 CPUs are allowed to enter idle state even if they have RCU
> > callbacks queued, see commit c0f4dfd4f90f1667d234d21f15153ea09a2eaa66
> > ("rcu: Make RCU_FAST_NO_HZ take advantage of numbered callbacks").
> > That change caused problems with nvidia proprietary driver which calls
> > acpi_os_map/unmap_generic_address several times during initialization.
> > Each unmap calls synchronize_rcu and adds significant delay. Totally
> > initialization is slowed for a couple of seconds and that is enough to
> > trigger timeout in hardware, gpu decides to "fell off the bus". Widely
> > spread workaround is reducing "rcu_idle_gp_delay" from 4 to 1 jiffy.
> >
> > This patch replaces synchronize_rcu() with synchronize_rcu_expedited()
> > which is much faster.
> >
> > Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
> > Reported-and-tested-by: Alexander Monakov <amonakov@gmail.com>
> > Cc: Tom Boshoven <tomboshoven@gmail.com>
> > Link: https://devtalk.nvidia.com/default/topic/567297/linux/linux-3-10-driver-crash/
>
> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Patch queued up for 3.19, thanks!

>
> > ---
> > drivers/acpi/osl.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> > index 9964f70..217713c 100644
> > --- a/drivers/acpi/osl.c
> > +++ b/drivers/acpi/osl.c
> > @@ -436,7 +436,7 @@ static void acpi_os_drop_map_ref(struct acpi_ioremap *map)
> > static void acpi_os_map_cleanup(struct acpi_ioremap *map)
> > {
> > if (!map->refcount) {
> > - synchronize_rcu();
> > + synchronize_rcu_expedited();
> > acpi_unmap(map->phys, map->virt);
> > kfree(map);
> > }
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.tux.org/lkml/
> >
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html

--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.


\
 
 \ /
  Last update: 2014-11-15 00:01    [W:0.082 / U:0.252 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site