linux-kernel - [tip: sched/core] softirq: use bit waits instead of var waits.

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Message-ID: <172837418103.1442.7837579642724319886.tip-bot2@tip-bot2>
Date: Tue, 08 Oct 2024 07:56:21 -0000
From: "tip-bot2 for NeilBrown" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: NeilBrown <neilb@...e.de>, "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: sched/core] softirq: use bit waits instead of var waits.

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     49994911b401c5f6b979060ffbc834949a024d8a
Gitweb:        https://git.kernel.org/tip/49994911b401c5f6b979060ffbc834949a024d8a
Author:        NeilBrown <neilb@...e.de>
AuthorDate:    Wed, 25 Sep 2024 15:31:44 +10:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 07 Oct 2024 09:28:39 +02:00

softirq: use bit waits instead of var waits.

The waiting in softirq.c is always waiting for a bit to be cleared.
This makes the bit wait functions seem more suitable.
By switching over we can rid of all explicit barriers.  We also use
wait_on_bit_lock() to avoid an explicit loop.

Signed-off-by: NeilBrown <neilb@...e.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lore.kernel.org/r/20240925053405.3960701-8-neilb@suse.de
---
 kernel/softirq.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index d082e78..b756d6b 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -748,10 +748,8 @@ EXPORT_SYMBOL(__tasklet_hi_schedule);
 
 static bool tasklet_clear_sched(struct tasklet_struct *t)
 {
-	if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) {
-		wake_up_var(&t->state);
+	if (test_and_clear_wake_up_bit(TASKLET_STATE_SCHED, &t->state))
 		return true;
-	}
 
 	WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n",
 		  t->use_callback ? "callback" : "func",
@@ -871,8 +869,7 @@ void tasklet_kill(struct tasklet_struct *t)
 	if (in_interrupt())
 		pr_notice("Attempt to kill tasklet from interrupt\n");
 
-	while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state))
-		wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state));
+	wait_on_bit_lock(&t->state, TASKLET_STATE_SCHED, TASK_UNINTERRUPTIBLE);
 
 	tasklet_unlock_wait(t);
 	tasklet_clear_sched(t);
@@ -882,16 +879,13 @@ EXPORT_SYMBOL(tasklet_kill);
 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
 void tasklet_unlock(struct tasklet_struct *t)
 {
-	smp_mb__before_atomic();
-	clear_bit(TASKLET_STATE_RUN, &t->state);
-	smp_mb__after_atomic();
-	wake_up_var(&t->state);
+	clear_and_wake_up_bit(TASKLET_STATE_RUN, &t->state);
 }
 EXPORT_SYMBOL_GPL(tasklet_unlock);
 
 void tasklet_unlock_wait(struct tasklet_struct *t)
 {
-	wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state));
+	wait_on_bit(&t->state, TASKLET_STATE_RUN, TASK_UNINTERRUPTIBLE);
 }
 EXPORT_SYMBOL_GPL(tasklet_unlock_wait);
 #endif