| Message ID | 20190814104131.20190-2-mark.rutland@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | kthread detection cleanup | expand |
Hi Mark, On Wed, Aug 14, 2019 at 12:43 PM Mark Rutland <mark.rutland@arm.com> 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 <mark.rutland@arm.com> 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 -- geert@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
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 <mark.rutland@arm.com> 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 <mark.rutland@arm.com> > > 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.
* Mark Rutland <mark.rutland@arm.com> 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 <mark.rutland@arm.com> 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 <mark.rutland@arm.com> > > > > 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
On Mon, Aug 19, 2019 at 10:52:13AM +0200, Ingo Molnar wrote: > * Mark Rutland <mark.rutland@arm.com> 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 <mark.rutland@arm.com> 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.
diff --git a/include/linux/sched.h b/include/linux/sched.h index 9f51932bd543..b7e96409d75f 100644 --- 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); +} + extern struct task_struct *curr_task(int cpu); extern void ia64_set_curr_task(int cpu, struct task_struct *p);
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 <mark.rutland@arm.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> --- include/linux/sched.h | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) -- 2.11.0