Re: Reading EeePC900 battery info causes stalls

[Alexey Starikovskiy <aystarik@gmail.com>]

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Alexey Starikovskiy wrote:
> Sitsofe Wheeler wrote:
>> Hi Alexey,
>>
>> Alexey Starikovskiy wrote:
>>> I think the least troubling place to add cond_resched() is then 
>>> ACPICA is exiting interpreter.
>>> Please check if the attached patch helps with latencies.
>>
>> There was no real change (latency was still bad). If you look at the 
>> trace (before your patch) on 
>> http://sucs.org/~sits/test/eeepc-debug/20080923/latency_trace.gz 
>> (700kbyte compressed, 15Mbytes uncompressed) you can see that 
>> acpi_ex_exit_interpreter is only called once near the end of the trace:
>>
>>      cat-5901    0.N.. 270496us : acpi_ex_exit_interpreter 
>> (acpi_ev_address_space_dispatch)
>>
>> By then the time had already been racked up...
>>
> Ok, let's add it to the end of acpi_ps_complete_op() then... They 
> appear every 100usec or so...
>
acpi_ps_parse_aml() is called not so often (~10000usec), so maybe it is 
a "sweet spot"



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diff --git a/drivers/acpi/parser/psparse.c b/drivers/acpi/parser/psparse.c
index 15e1702..ceab67c 100644
--- a/drivers/acpi/parser/psparse.c
+++ b/drivers/acpi/parser/psparse.c
@@ -439,6 +439,8 @@ acpi_ps_next_parse_state(struct acpi_walk_state *walk_state,
  *
  ******************************************************************************/
 
+#include <linux/sched.h>
+
 acpi_status acpi_ps_parse_aml(struct acpi_walk_state *walk_state)
 {
 	acpi_status status;
@@ -688,5 +690,6 @@ acpi_status acpi_ps_parse_aml(struct acpi_walk_state *walk_state)
 	acpi_ut_delete_generic_state(ACPI_CAST_PTR
 				     (union acpi_generic_state, thread));
 	acpi_gbl_current_walk_list = prev_walk_list;
+	cond_resched();
 	return_ACPI_STATUS(status);
 }