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rcu: Fix idle-task checks 

RCU has traditionally relied on idle_cpu() to determine whether a given
CPU is running in the context of an idle task, but commit 908a3283
(Fix idle_cpu()) has invalidated this approach.  After commit 908a3283,
idle_cpu() will return true if the current CPU is currently running the
idle task, and will be doing so for the foreseeable future.  RCU instead
needs to know whether or not the current CPU is currently running the
idle task, regardless of what the near future might bring.

This commit therefore switches from idle_cpu() to "current->pid != 0".

Reported-by: Wu Fengguang <fengguang.wu@intel.com>
Suggested-by: Carsten Emde <C.Emde@osadl.org>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Tested-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2011-11-02 07:38:25 -07:00 committed by Paul E. McKenney
parent aea1b35e29
commit 11dbaa8cb7
2 changed files with 4 additions and 4 deletions
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4
kernel/rcutiny.c
View File

@ -64,7 +64,7 @@ static void rcu_idle_enter_common(long long oldval)
return;
}
RCU_TRACE(trace_rcu_dyntick("Start", oldval, rcu_dynticks_nesting));
if (!idle_cpu(smp_processor_id())) {
if (current->pid != 0) {
struct task_struct *idle = idle_task(smp_processor_id());
RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task",
@ -118,7 +118,7 @@ static void rcu_idle_exit_common(long long oldval)
return;
}
RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting));
if (!idle_cpu(smp_processor_id())) {
if (current->pid != 0) {
struct task_struct *idle = idle_task(smp_processor_id());
RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task",

4
kernel/rcutree.c
View File

@ -355,7 +355,7 @@ static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval)
return;
}
trace_rcu_dyntick("Start", oldval, rdtp->dynticks_nesting);
if (!idle_cpu(smp_processor_id())) {
if (current->pid != 0) {
struct task_struct *idle = idle_task(smp_processor_id());
trace_rcu_dyntick("Error on entry: not idle task",
@ -449,7 +449,7 @@ static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval)
smp_mb__after_atomic_inc(); /* See above. */
WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting);
if (!idle_cpu(smp_processor_id())) {
if (current->pid != 0) {
struct task_struct *idle = idle_task(smp_processor_id());
trace_rcu_dyntick("Error on exit: not idle task",