| Message ID | 1321388885-11211-4-git-send-email-paulmck@linux.vnet.ibm.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Nov 15, 2011 at 12:28:00PM -0800, Paul E. McKenney wrote: > From: Paul E. McKenney <paul.mckenney@linaro.org> > > Commit 908a3283 (Fix idle_cpu()) invalidated some uses of idle_cpu(), > which used to say whether or not the CPU was running the idle task, > but now instead says whether or not the CPU is running the idle task > in the absence of pending wakeups. Although this new implementation > gives a better answer to the question "is this CPU idle?", it also > invalidates other uses that were made of idle_cpu(). > > This commit therefore introduces a new is_idle_task() API member > that determines whether or not the specified task is one of the > idle tasks, allowing open-coded "->pid == 0" sequences to be replaced > by something more meaningful. > > Suggested-by: Josh Triplett <josh@joshtriplett.org> > Suggested-by: Peter Zijlstra <peterz@infradead.org> > Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > --- > include/linux/sched.h | 1 + > kernel/sched.c | 9 +++++++++ > 2 files changed, 10 insertions(+), 0 deletions(-) > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 68daf4f..4b1077b 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -2071,6 +2071,7 @@ extern int sched_setscheduler(struct task_struct *, int, > extern int sched_setscheduler_nocheck(struct task_struct *, int, > const struct sched_param *); > extern struct task_struct *idle_task(int cpu); > +extern int is_idle_task(struct task_struct *p); The kernel has a bool type; please use it here rather than int, to make the return value more obvious. Also, any particular reason not to make this a static inline? - Josh Triplett
On Tue, Nov 15, 2011 at 01:13:02PM -0800, Josh Triplett wrote: > On Tue, Nov 15, 2011 at 12:28:00PM -0800, Paul E. McKenney wrote: > > From: Paul E. McKenney <paul.mckenney@linaro.org> > > > > Commit 908a3283 (Fix idle_cpu()) invalidated some uses of idle_cpu(), > > which used to say whether or not the CPU was running the idle task, > > but now instead says whether or not the CPU is running the idle task > > in the absence of pending wakeups. Although this new implementation > > gives a better answer to the question "is this CPU idle?", it also > > invalidates other uses that were made of idle_cpu(). > > > > This commit therefore introduces a new is_idle_task() API member > > that determines whether or not the specified task is one of the > > idle tasks, allowing open-coded "->pid == 0" sequences to be replaced > > by something more meaningful. > > > > Suggested-by: Josh Triplett <josh@joshtriplett.org> > > Suggested-by: Peter Zijlstra <peterz@infradead.org> > > Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > --- > > include/linux/sched.h | 1 + > > kernel/sched.c | 9 +++++++++ > > 2 files changed, 10 insertions(+), 0 deletions(-) > > > > diff --git a/include/linux/sched.h b/include/linux/sched.h > > index 68daf4f..4b1077b 100644 > > --- a/include/linux/sched.h > > +++ b/include/linux/sched.h > > @@ -2071,6 +2071,7 @@ extern int sched_setscheduler(struct task_struct *, int, > > extern int sched_setscheduler_nocheck(struct task_struct *, int, > > const struct sched_param *); > > extern struct task_struct *idle_task(int cpu); > > +extern int is_idle_task(struct task_struct *p); > > The kernel has a bool type; please use it here rather than int, to make > the return value more obvious. > > Also, any particular reason not to make this a static inline? That does work for all the uses thus far, so made both suggested changes. Thanx, Paul
diff --git a/include/linux/sched.h b/include/linux/sched.h index 68daf4f..4b1077b 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2071,6 +2071,7 @@ extern int sched_setscheduler(struct task_struct *, int, extern int sched_setscheduler_nocheck(struct task_struct *, int, const struct sched_param *); extern struct task_struct *idle_task(int cpu); +extern int is_idle_task(struct task_struct *p); extern struct task_struct *curr_task(int cpu); extern void set_curr_task(int cpu, struct task_struct *p); diff --git a/kernel/sched.c b/kernel/sched.c index 0e9344a..c9c1bb3 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -5185,6 +5185,15 @@ struct task_struct *idle_task(int cpu) } /** + * is_idle_task - is the specified task an idle task? + * @tsk: the task in question. + */ +int is_idle_task(struct task_struct *p) +{ + return p->pid == 0; +} + +/** * find_process_by_pid - find a process with a matching PID value. * @pid: the pid in question. */