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 c0f4dfd4f9
("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>
This commit is contained in:
parent
206c5f60a3
commit
74b51ee152
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@ -436,7 +436,7 @@ static void acpi_os_drop_map_ref(struct acpi_ioremap *map)
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static void acpi_os_map_cleanup(struct acpi_ioremap *map)
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{
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if (!map->refcount) {
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synchronize_rcu();
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synchronize_rcu_expedited();
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acpi_unmap(map->phys, map->virt);
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kfree(map);
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}
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