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sched,rcu: Rework try_invoke_on_locked_down_task()

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Give try_invoke_on_locked_down_task() a saner name and have it return
an int so that the caller might distinguish between different reasons
of failure.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com> # on s390
Link: https://lkml.kernel.org/r/20210929152428.649944917@infradead.org
This commit is contained in:
Peter Zijlstra 2021-09-21 21:54:32 +02:00
parent f6ac18fafc
commit 9b3c4ab304
4 changed files with 15 additions and 14 deletions
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3
include/linux/wait.h
View file

@ -1160,6 +1160,7 @@ int autoremove_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, i
(wait)->flags = 0; \
} while (0)
bool try_invoke_on_locked_down_task(struct task_struct *p, bool (*func)(struct task_struct *t, void *arg), void *arg);
typedef int (*task_call_f)(struct task_struct *p, void *arg);
extern int task_call_func(struct task_struct *p, task_call_f func, void *arg);
#endif /* _LINUX_WAIT_H */

12
kernel/rcu/tasks.h
View file

@ -928,7 +928,7 @@ static void trc_read_check_handler(void *t_in)
}
/* Callback function for scheduler to check locked-down task. */
static bool trc_inspect_reader(struct task_struct *t, void *arg)
static int trc_inspect_reader(struct task_struct *t, void *arg)
{
int cpu = task_cpu(t);
bool in_qs = false;
@ -939,7 +939,7 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg)
// If no chance of heavyweight readers, do it the hard way.
if (!ofl && !IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB))
return false;
return -EINVAL;
// If heavyweight readers are enabled on the remote task,
// we can inspect its state despite its currently running.
@ -947,7 +947,7 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg)
n_heavy_reader_attempts++;
if (!ofl && // Check for "running" idle tasks on offline CPUs.
!rcu_dynticks_zero_in_eqs(cpu, &t->trc_reader_nesting))
return false; // No quiescent state, do it the hard way.
return -EINVAL; // No quiescent state, do it the hard way.
n_heavy_reader_updates++;
if (ofl)
n_heavy_reader_ofl_updates++;
@ -962,7 +962,7 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg)
t->trc_reader_checked = true;
if (in_qs)
return true; // Already in quiescent state, done!!!
return 0; // Already in quiescent state, done!!!
// The task is in a read-side critical section, so set up its
// state so that it will awaken the grace-period kthread upon exit
@ -970,7 +970,7 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg)
atomic_inc(&trc_n_readers_need_end); // One more to wait on.
WARN_ON_ONCE(READ_ONCE(t->trc_reader_special.b.need_qs));
WRITE_ONCE(t->trc_reader_special.b.need_qs, true);
return true;
return 0;
}
/* Attempt to extract the state for the specified task. */
@ -992,7 +992,7 @@ static void trc_wait_for_one_reader(struct task_struct *t,
// Attempt to nail down the task for inspection.
get_task_struct(t);
if (try_invoke_on_locked_down_task(t, trc_inspect_reader, NULL)) {
if (!task_call_func(t, trc_inspect_reader, NULL)) {
put_task_struct(t);
return;
}

8
kernel/rcu/tree_stall.h
View file

@ -240,16 +240,16 @@ struct rcu_stall_chk_rdr {
* Report out the state of a not-running task that is stalling the
* current RCU grace period.
*/
static bool check_slow_task(struct task_struct *t, void *arg)
static int check_slow_task(struct task_struct *t, void *arg)
{
struct rcu_stall_chk_rdr *rscrp = arg;
if (task_curr(t))
return false; // It is running, so decline to inspect it.
return -EBUSY; // It is running, so decline to inspect it.
rscrp->nesting = t->rcu_read_lock_nesting;
rscrp->rs = t->rcu_read_unlock_special;
rscrp->on_blkd_list = !list_empty(&t->rcu_node_entry);
return true;
return 0;
}
/*
@ -283,7 +283,7 @@ static int rcu_print_task_stall(struct rcu_node *rnp, unsigned long flags)
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
while (i) {
t = ts[--i];
if (!try_invoke_on_locked_down_task(t, check_slow_task, &rscr))
if (task_call_func(t, check_slow_task, &rscr))
pr_cont(" P%d", t->pid);
else
pr_cont(" P%d/%d:%c%c%c%c",

6
kernel/sched/core.c
View file

@ -4110,7 +4110,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
}
/**
* try_invoke_on_locked_down_task - Invoke a function on task in fixed state
* task_call_func - Invoke a function on task in fixed state
* @p: Process for which the function is to be invoked, can be @current.
* @func: Function to invoke.
* @arg: Argument to function.
@ -4123,12 +4123,12 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
* Returns:
* Whatever @func returns
*/
bool try_invoke_on_locked_down_task(struct task_struct *p, bool (*func)(struct task_struct *t, void *arg), void *arg)
int task_call_func(struct task_struct *p, task_call_f func, void *arg)
{
struct rq *rq = NULL;
unsigned int state;
struct rq_flags rf;
bool ret = false;
int ret;
raw_spin_lock_irqsave(&p->pi_lock, rf.flags);