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| author | Konstantin Khlebnikov <koct9i@gmail.com> | 2014-11-09 12:53:37 +0300 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2014-11-11 23:44:58 +0300 |
| commit | 74b51ee152b6d99e61ba329799a039453fb9438f (patch) | |
| tree | 72af2fb275b014f71622ad45526d5e0d30b42188 /drivers/acpi | |
| parent | 206c5f60a3d902bc4b56dab2de3e88de5eb06108 (diff) | |
| download | linux-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.c | 2 |
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); } |