Re: [PATCH 1/9] sched/core: add is_kthread() helper
On Mon, Aug 19, 2019 at 10:52:13AM +0200, Ingo Molnar wrote:
> * Mark Rutland wrote:
> > On Wed, Aug 14, 2019 at 01:26:43PM +0200, Geert Uytterhoeven wrote:
> > > On Wed, Aug 14, 2019 at 12:43 PM Mark Rutland
> > > wrote:
> > > > +static inline bool is_kthread(const struct task_struct *p)
> > > > +{
> > > > + return !!(p->flags & PF_KTHREAD);
> > >
> > > The !! is not really needed.
> > > Probably you followed is_idle_task() above (where it's also not needed).
> >
> > Indeed! I'm aware of the implicit bool conversion, but kept that for
> > consistency.
> >
> > Peter, Ingo, do you have a preference?
>
> So the !! pattern is useful where the return value is an integer (i.e.
> there's a risk of non-bool use) - but the return value is an explicit
> bool here, so !! is IMO an entirely superfluous obfuscation.
Yeah, no real preference, for giggles, (_Bool) also seems to work.
Re: [PATCH 1/9] sched/core: add is_kthread() helper
* Mark Rutland wrote:
> On Wed, Aug 14, 2019 at 01:26:43PM +0200, Geert Uytterhoeven wrote:
> > Hi Mark,
> >
> > On Wed, Aug 14, 2019 at 12:43 PM Mark Rutland wrote:
> > > Code checking whether a task is a kthread isn't very consistent. Some
> > > code correctly tests task->flags & PF_THREAD, while other code checks
> > > task->mm (which can be true for a kthread which calls use_mm()).
> > >
> > > So that we can clean this up and keep the code easy to follow, let's add
> > > an obvious helper function to test whether a task is a kthread.
> > > Subsequent patches will use this as part of cleaning up and correcting
> > > open-coded tests.
> > >
> > > At the same time, let's fix up the kerneldoc for is_idle_task() for
> > > consistency with the new helper, using true/false rather than 0/1, given
> > > the functions return bool.
> > >
> > > Signed-off-by: Mark Rutland
> >
> > Thanks for your patch!
> >
> > > --- a/include/linux/sched.h
> > > +++ b/include/linux/sched.h
> > > @@ -1621,13 +1621,24 @@ extern struct task_struct *idle_task(int cpu);
> > > * is_idle_task - is the specified task an idle task?
> > > * @p: the task in question.
> > > *
> > > - * Return: 1 if @p is an idle task. 0 otherwise.
> > > + * Return: true if @p is an idle task, false otherwise.
> > > */
> > > static inline bool is_idle_task(const struct task_struct *p)
> > > {
> > > return !!(p->flags & PF_IDLE);
> > > }
> > >
> > > +/**
> > > + * is_kthread - is the specified task a kthread
> > > + * @p: the task in question.
> > > + *
> > > + * Return: true if @p is a kthread, false otherwise.
> > > + */
> > > +static inline bool is_kthread(const struct task_struct *p)
> > > +{
> > > + return !!(p->flags & PF_KTHREAD);
> >
> > The !! is not really needed.
> > Probably you followed is_idle_task() above (where it's also not needed).
>
> Indeed! I'm aware of the implicit bool conversion, but kept that for
> consistency.
>
> Peter, Ingo, do you have a preference?
So the !! pattern is useful where the return value is an integer (i.e.
there's a risk of non-bool use) - but the return value is an explicit
bool here, so !! is IMO an entirely superfluous obfuscation.
Should probably be fixed for is_idle_task() as well?
Thanks,
Ingo
Re: [PATCH 1/9] sched/core: add is_kthread() helper
On Wed, Aug 14, 2019 at 01:26:43PM +0200, Geert Uytterhoeven wrote:
> Hi Mark,
>
> On Wed, Aug 14, 2019 at 12:43 PM Mark Rutland wrote:
> > Code checking whether a task is a kthread isn't very consistent. Some
> > code correctly tests task->flags & PF_THREAD, while other code checks
> > task->mm (which can be true for a kthread which calls use_mm()).
> >
> > So that we can clean this up and keep the code easy to follow, let's add
> > an obvious helper function to test whether a task is a kthread.
> > Subsequent patches will use this as part of cleaning up and correcting
> > open-coded tests.
> >
> > At the same time, let's fix up the kerneldoc for is_idle_task() for
> > consistency with the new helper, using true/false rather than 0/1, given
> > the functions return bool.
> >
> > Signed-off-by: Mark Rutland
>
> Thanks for your patch!
>
> > --- a/include/linux/sched.h
> > +++ b/include/linux/sched.h
> > @@ -1621,13 +1621,24 @@ extern struct task_struct *idle_task(int cpu);
> > * is_idle_task - is the specified task an idle task?
> > * @p: the task in question.
> > *
> > - * Return: 1 if @p is an idle task. 0 otherwise.
> > + * Return: true if @p is an idle task, false otherwise.
> > */
> > static inline bool is_idle_task(const struct task_struct *p)
> > {
> > return !!(p->flags & PF_IDLE);
> > }
> >
> > +/**
> > + * is_kthread - is the specified task a kthread
> > + * @p: the task in question.
> > + *
> > + * Return: true if @p is a kthread, false otherwise.
> > + */
> > +static inline bool is_kthread(const struct task_struct *p)
> > +{
> > + return !!(p->flags & PF_KTHREAD);
>
> The !! is not really needed.
> Probably you followed is_idle_task() above (where it's also not needed).
Indeed! I'm aware of the implicit bool conversion, but kept that for
consistency.
Peter, Ingo, do you have a preference?
Thanks,
Mark.
Re: [PATCH 1/9] sched/core: add is_kthread() helper
Hi Mark,
On Wed, Aug 14, 2019 at 12:43 PM Mark Rutland wrote:
> Code checking whether a task is a kthread isn't very consistent. Some
> code correctly tests task->flags & PF_THREAD, while other code checks
> task->mm (which can be true for a kthread which calls use_mm()).
>
> So that we can clean this up and keep the code easy to follow, let's add
> an obvious helper function to test whether a task is a kthread.
> Subsequent patches will use this as part of cleaning up and correcting
> open-coded tests.
>
> At the same time, let's fix up the kerneldoc for is_idle_task() for
> consistency with the new helper, using true/false rather than 0/1, given
> the functions return bool.
>
> Signed-off-by: Mark Rutland
Thanks for your patch!
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1621,13 +1621,24 @@ extern struct task_struct *idle_task(int cpu);
> * is_idle_task - is the specified task an idle task?
> * @p: the task in question.
> *
> - * Return: 1 if @p is an idle task. 0 otherwise.
> + * Return: true if @p is an idle task, false otherwise.
> */
> static inline bool is_idle_task(const struct task_struct *p)
> {
> return !!(p->flags & PF_IDLE);
> }
>
> +/**
> + * is_kthread - is the specified task a kthread
> + * @p: the task in question.
> + *
> + * Return: true if @p is a kthread, false otherwise.
> + */
> +static inline bool is_kthread(const struct task_struct *p)
> +{
> + return !!(p->flags & PF_KTHREAD);
The !! is not really needed.
Probably you followed is_idle_task() above (where it's also not needed).
> +}
> +
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
