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From: Peter Zijlstra <peterz@infradead.org>
To: gor@linux.ibm.com, jpoimboe@redhat.com, jikos@kernel.org,
	mbenes@suse.cz, pmladek@suse.com, mingo@kernel.org
Cc: linux-kernel@vger.kernel.org, peterz@infradead.org,
	joe.lawrence@redhat.com, fweisbec@gmail.com, tglx@linutronix.de,
	hca@linux.ibm.com, svens@linux.ibm.com, sumanthk@linux.ibm.com,
	live-patching@vger.kernel.org, paulmck@kernel.org,
	rostedt@goodmis.org, x86@kernel.org
Subject: [PATCH v2 02/11] sched,rcu: Rework try_invoke_on_locked_down_task()
Date: Wed, 29 Sep 2021 17:17:25 +0200	[thread overview]
Message-ID: <20210929152428.649944917@infradead.org> (raw)
In-Reply-To: <20210929151723.162004989@infradead.org>

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>
---
 include/linux/wait.h    |    3 ++-
 kernel/rcu/tasks.h      |   12 ++++++------
 kernel/rcu/tree_stall.h |    8 ++++----
 kernel/sched/core.c     |    6 +++---
 4 files changed, 15 insertions(+), 14 deletions(-)

--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -1160,6 +1160,7 @@ int autoremove_wake_function(struct wait
 		(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 */
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -928,7 +928,7 @@ static void trc_read_check_handler(void
 }
 
 /* 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 ta
 
 		// 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 ta
 		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 ta
 	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 ta
 	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(stru
 
 	// 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;
 	}
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -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 r
 	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",
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4106,7 +4106,7 @@ try_to_wake_up(struct task_struct *p, un
 }
 
 /**
- * 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.
@@ -4119,12 +4119,12 @@ try_to_wake_up(struct task_struct *p, un
  * 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);
 



  parent reply	other threads:[~2021-09-29 16:08 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-29 15:17 [PATCH v2 00/11] sched,rcu,context_tracking,livepatch: Improve livepatch task transitions for idle and NOHZ_FULL Peter Zijlstra
2021-09-29 15:17 ` [PATCH v2 01/11] sched: Improve try_invoke_on_locked_down_task() Peter Zijlstra
2021-09-29 15:17 ` Peter Zijlstra [this message]
2021-09-29 15:17 ` [PATCH v2 03/11] sched,livepatch: Use task_call_func() Peter Zijlstra
2021-10-05 11:40   ` Petr Mladek
2021-10-05 14:03     ` Peter Zijlstra
2021-10-06  8:59   ` Miroslav Benes
2021-09-29 15:17 ` [PATCH v2 04/11] sched: Simplify wake_up_*idle*() Peter Zijlstra
2021-10-13 14:32   ` Qian Cai
2021-10-19  3:47     ` Qian Cai
2021-10-19  8:56       ` Peter Zijlstra
2021-10-19  9:10         ` Peter Zijlstra
2021-10-19 15:32           ` Qian Cai
2021-10-19 15:50             ` Peter Zijlstra
2021-10-19 19:22               ` Qian Cai
2021-10-19 20:27                 ` Peter Zijlstra
     [not found]   ` <CGME20211022134630eucas1p2e79e2816587d182c580459d567c1f2a9@eucas1p2.samsung.com>
2021-10-22 13:46     ` Marek Szyprowski
2021-09-29 15:17 ` [PATCH v2 05/11] sched,livepatch: Use wake_up_if_idle() Peter Zijlstra
2021-10-05 12:00   ` Petr Mladek
2021-10-06  9:16   ` Miroslav Benes
2021-10-07  9:18     ` Vasily Gorbik
2021-10-07 10:02       ` Peter Zijlstra
2021-10-13 19:37   ` Arnd Bergmann
2021-10-14 10:42     ` Peter Zijlstra
2021-09-29 15:17 ` [RFC][PATCH v2 06/11] context_tracking: Prefix user_{enter,exit}*() Peter Zijlstra
2021-09-29 15:17 ` [RFC][PATCH v2 07/11] context_tracking: Add an atomic sequence/state count Peter Zijlstra
2021-09-29 15:17 ` [RFC][PATCH v2 08/11] context_tracking,rcu: Replace RCU dynticks counter with context_tracking Peter Zijlstra
2021-09-29 18:37   ` Paul E. McKenney
2021-09-29 19:09     ` Peter Zijlstra
2021-09-29 19:11     ` Peter Zijlstra
2021-09-29 19:13     ` Peter Zijlstra
2021-09-29 19:24       ` Peter Zijlstra
2021-09-29 19:45         ` Paul E. McKenney
2021-09-29 18:54   ` Peter Zijlstra
2021-09-29 15:17 ` [RFC][PATCH v2 09/11] context_tracking,livepatch: Dont disturb NOHZ_FULL Peter Zijlstra
2021-10-06  8:12   ` Petr Mladek
2021-10-06  9:04     ` Peter Zijlstra
2021-10-06 10:29       ` Petr Mladek
2021-10-06 11:41         ` Peter Zijlstra
2021-10-06 11:48         ` Miroslav Benes
2021-09-29 15:17 ` [RFC][PATCH v2 10/11] livepatch: Remove klp_synchronize_transition() Peter Zijlstra
2021-10-06 12:30   ` Petr Mladek
2021-09-29 15:17 ` [RFC][PATCH v2 11/11] context_tracking,x86: Fix text_poke_sync() vs NOHZ_FULL Peter Zijlstra
2021-10-21 18:39   ` Marcelo Tosatti
2021-10-21 18:40     ` Marcelo Tosatti
2021-10-21 19:25     ` Peter Zijlstra
2021-10-21 19:57       ` Marcelo Tosatti
2021-10-21 20:18         ` Peter Zijlstra
2021-10-26 18:19           ` Marcelo Tosatti
2021-10-26 19:38             ` Peter Zijlstra
2021-09-29 18:03 ` [PATCH v2 00/11] sched,rcu,context_tracking,livepatch: Improve livepatch task transitions for idle and NOHZ_FULL Paul E. McKenney

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