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authorKonstantin Khlebnikov <koct9i@gmail.com>2014-11-09 12:53:37 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-11-11 23:44:58 +0300
commit74b51ee152b6d99e61ba329799a039453fb9438f (patch)
tree72af2fb275b014f71622ad45526d5e0d30b42188 /drivers/acpi
parent206c5f60a3d902bc4b56dab2de3e88de5eb06108 (diff)
downloadlinux-74b51ee152b6d99e61ba329799a039453fb9438f.tar.xz
ACPI / osl: speedup grace period in acpi_os_map_cleanup
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. Link: https://devtalk.nvidia.com/default/topic/567297/linux/linux-3-10-driver-crash/ Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com> Reported-and-tested-by: Alexander Monakov <amonakov@gmail.com> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/acpi')
-rw-r--r--drivers/acpi/osl.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 9964f70be98d..217713c11aaa 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);
}