| Message ID | 20240711130004.2157737-4-vschneid@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | sched/fair: Defer CFS throttle to user entry | expand |
On 07/11, Valentin Schneider wrote: > > Later commits will need to issue a task_work_cancel() from within the > scheduler with the task's ->pi_lock held. > > Add a _locked variant that expects p->pi_lock to be held. Expose it in a > separate scheduler header file, as this really is a scheduler-only > interface. > > Signed-off-by: Valentin Schneider <vschneid@redhat.com> > --- > kernel/sched/task_work_sched.h | 14 +++++++ > kernel/task_work.c | 67 ++++++++++++++++++++++++++-------- > 2 files changed, 66 insertions(+), 15 deletions(-) > create mode 100644 kernel/sched/task_work_sched.h I am not sure the new task_work_sched.h makes sense, but I won't argue. Reviewed-by: Oleg Nesterov <oleg@redhat.com>
On Thu, Jul 11, 2024 at 02:59:57PM +0200, Valentin Schneider wrote: > Later commits will need to issue a task_work_cancel() from within the > scheduler with the task's ->pi_lock held. > > Add a _locked variant that expects p->pi_lock to be held. Expose it in a > separate scheduler header file, as this really is a scheduler-only > interface. > > Signed-off-by: Valentin Schneider <vschneid@redhat.com> > --- > kernel/sched/task_work_sched.h | 14 +++++++ > kernel/task_work.c | 67 ++++++++++++++++++++++++++-------- > 2 files changed, 66 insertions(+), 15 deletions(-) > create mode 100644 kernel/sched/task_work_sched.h > > diff --git a/kernel/sched/task_work_sched.h b/kernel/sched/task_work_sched.h > new file mode 100644 > index 0000000000000..e235da456427f > --- /dev/null > +++ b/kernel/sched/task_work_sched.h > @@ -0,0 +1,14 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +/* > + * Scheduler internal task_work methods > + */ > +#ifndef _KERNEL_TASK_WORK_SCHED_H > +#define _KERNEL_TASK_WORK_SCHED_H > + > +#include <linux/task_work.h> > +#include <linux/sched.h> > + > +struct callback_head * > +task_work_cancel_locked(struct task_struct *task, task_work_func_t func); > + > +#endif Do we really need that exposed? Can't we squirrel that way in kernel/sched/sched.h and forget about it? > @@ -74,33 +76,20 @@ int task_work_add(struct task_struct *task, struct callback_head *work, > return 0; > } > > -/** > - * task_work_cancel_match - cancel a pending work added by task_work_add() > - * @task: the task which should execute the work > - * @match: match function to call > - * @data: data to be passed in to match function > - * > - * RETURNS: > - * The found work or NULL if not found. > - */ > -struct callback_head * > -task_work_cancel_match(struct task_struct *task, > +static struct callback_head * > +task_work_cancel_match_locked(struct task_struct *task, > bool (*match)(struct callback_head *, void *data), > void *data) > { > struct callback_head **pprev = &task->task_works; > struct callback_head *work; > - unsigned long flags; > > - if (likely(!task_work_pending(task))) > - return NULL; > /* > * If cmpxchg() fails we continue without updating pprev. > * Either we raced with task_work_add() which added the > * new entry before this work, we will find it again. Or > * we raced with task_work_run(), *pprev == NULL/exited. > */ > - raw_spin_lock_irqsave(&task->pi_lock, flags); > work = READ_ONCE(*pprev); > while (work) { > if (!match(work, data)) { > @@ -109,6 +98,32 @@ task_work_cancel_match(struct task_struct *task, > } else if (try_cmpxchg(pprev, &work, work->next)) > break; > } > + > + return work; > +} > @@ -136,6 +151,28 @@ task_work_cancel(struct task_struct *task, task_work_func_t func) > return task_work_cancel_match(task, task_work_func_match, func); > } > > +/** > + * task_work_cancel - cancel a pending work added by task_work_add() > + * @task: the task which should execute the work > + * @func: identifies the work to remove > + * > + * Find the last queued pending work with ->func == @func and remove > + * it from queue. > + * > + * RETURNS: > + * The found work or NULL if not found. > + */ > +struct callback_head * > +task_work_cancel_locked(struct task_struct *task, task_work_func_t func) > +{ > + lockdep_assert_held(&task->pi_lock); I'm thinking that lockde_assert wants to live in your _locked function above. > + if (likely(!task_work_pending(task))) > + return NULL; > + > + return task_work_cancel_match_locked(task, task_work_func_match, func); > +} > + > /** > * task_work_run - execute the works added by task_work_add() > * > -- > 2.43.0 >
On 12/07/24 17:20, Peter Zijlstra wrote: > On Thu, Jul 11, 2024 at 02:59:57PM +0200, Valentin Schneider wrote: >> Later commits will need to issue a task_work_cancel() from within the >> scheduler with the task's ->pi_lock held. >> >> Add a _locked variant that expects p->pi_lock to be held. Expose it in a >> separate scheduler header file, as this really is a scheduler-only >> interface. >> >> Signed-off-by: Valentin Schneider <vschneid@redhat.com> >> --- >> kernel/sched/task_work_sched.h | 14 +++++++ >> kernel/task_work.c | 67 ++++++++++++++++++++++++++-------- >> 2 files changed, 66 insertions(+), 15 deletions(-) >> create mode 100644 kernel/sched/task_work_sched.h >> >> diff --git a/kernel/sched/task_work_sched.h b/kernel/sched/task_work_sched.h >> new file mode 100644 >> index 0000000000000..e235da456427f >> --- /dev/null >> +++ b/kernel/sched/task_work_sched.h >> @@ -0,0 +1,14 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> +/* >> + * Scheduler internal task_work methods >> + */ >> +#ifndef _KERNEL_TASK_WORK_SCHED_H >> +#define _KERNEL_TASK_WORK_SCHED_H >> + >> +#include <linux/task_work.h> >> +#include <linux/sched.h> >> + >> +struct callback_head * >> +task_work_cancel_locked(struct task_struct *task, task_work_func_t func); >> + >> +#endif > > > Do we really need that exposed? Can't we squirrel that way in > kernel/sched/sched.h and forget about it? > Nah that's not required, I thought a clean cut header would be neater but given its single user, tossing that to sched.h looks better. >> +struct callback_head * >> +task_work_cancel_locked(struct task_struct *task, task_work_func_t func) >> +{ >> + lockdep_assert_held(&task->pi_lock); > > I'm thinking that lockde_assert wants to live in your _locked function > above. > Quite so!
diff --git a/kernel/sched/task_work_sched.h b/kernel/sched/task_work_sched.h new file mode 100644 index 0000000000000..e235da456427f --- /dev/null +++ b/kernel/sched/task_work_sched.h @@ -0,0 +1,14 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Scheduler internal task_work methods + */ +#ifndef _KERNEL_TASK_WORK_SCHED_H +#define _KERNEL_TASK_WORK_SCHED_H + +#include <linux/task_work.h> +#include <linux/sched.h> + +struct callback_head * +task_work_cancel_locked(struct task_struct *task, task_work_func_t func); + +#endif diff --git a/kernel/task_work.c b/kernel/task_work.c index 95a7e1b7f1dab..81092bc2e7371 100644 --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -3,6 +3,8 @@ #include <linux/task_work.h> #include <linux/resume_user_mode.h> +#include "sched/task_work_sched.h" + static struct callback_head work_exited; /* all we need is ->next == NULL */ /** @@ -74,33 +76,20 @@ int task_work_add(struct task_struct *task, struct callback_head *work, return 0; } -/** - * task_work_cancel_match - cancel a pending work added by task_work_add() - * @task: the task which should execute the work - * @match: match function to call - * @data: data to be passed in to match function - * - * RETURNS: - * The found work or NULL if not found. - */ -struct callback_head * -task_work_cancel_match(struct task_struct *task, +static struct callback_head * +task_work_cancel_match_locked(struct task_struct *task, bool (*match)(struct callback_head *, void *data), void *data) { struct callback_head **pprev = &task->task_works; struct callback_head *work; - unsigned long flags; - if (likely(!task_work_pending(task))) - return NULL; /* * If cmpxchg() fails we continue without updating pprev. * Either we raced with task_work_add() which added the * new entry before this work, we will find it again. Or * we raced with task_work_run(), *pprev == NULL/exited. */ - raw_spin_lock_irqsave(&task->pi_lock, flags); work = READ_ONCE(*pprev); while (work) { if (!match(work, data)) { @@ -109,6 +98,32 @@ task_work_cancel_match(struct task_struct *task, } else if (try_cmpxchg(pprev, &work, work->next)) break; } + + return work; +} + +/** + * task_work_cancel_match - cancel a pending work added by task_work_add() + * @task: the task which should execute the work + * @match: match function to call + * @data: data to be passed in to match function + * + * RETURNS: + * The found work or NULL if not found. + */ +struct callback_head * +task_work_cancel_match(struct task_struct *task, + bool (*match)(struct callback_head *, void *data), + void *data) +{ + unsigned long flags; + struct callback_head *work; + + if (likely(!task_work_pending(task))) + return NULL; + + raw_spin_lock_irqsave(&task->pi_lock, flags); + work = task_work_cancel_match_locked(task, match, data); raw_spin_unlock_irqrestore(&task->pi_lock, flags); return work; @@ -136,6 +151,28 @@ task_work_cancel(struct task_struct *task, task_work_func_t func) return task_work_cancel_match(task, task_work_func_match, func); } +/** + * task_work_cancel - cancel a pending work added by task_work_add() + * @task: the task which should execute the work + * @func: identifies the work to remove + * + * Find the last queued pending work with ->func == @func and remove + * it from queue. + * + * RETURNS: + * The found work or NULL if not found. + */ +struct callback_head * +task_work_cancel_locked(struct task_struct *task, task_work_func_t func) +{ + lockdep_assert_held(&task->pi_lock); + + if (likely(!task_work_pending(task))) + return NULL; + + return task_work_cancel_match_locked(task, task_work_func_match, func); +} + /** * task_work_run - execute the works added by task_work_add() *
Later commits will need to issue a task_work_cancel() from within the scheduler with the task's ->pi_lock held. Add a _locked variant that expects p->pi_lock to be held. Expose it in a separate scheduler header file, as this really is a scheduler-only interface. Signed-off-by: Valentin Schneider <vschneid@redhat.com> --- kernel/sched/task_work_sched.h | 14 +++++++ kernel/task_work.c | 67 ++++++++++++++++++++++++++-------- 2 files changed, 66 insertions(+), 15 deletions(-) create mode 100644 kernel/sched/task_work_sched.h