linux-kernel - [PATCH] semaphore: Add might_sleep() to down

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Message-ID: <20210809021215.19991-1-nixiaoming@huawei.com>
Date:   Mon, 9 Aug 2021 10:12:15 +0800
From:   Xiaoming Ni <nixiaoming@...wei.com>
To:     <linux-kernel@...r.kernel.org>, <peterz@...radead.org>,
        <mingo@...hat.com>, <will@...nel.org>, <longman@...hat.com>,
        <boqun.feng@...il.com>
CC:     <nixiaoming@...wei.com>, <wangle6@...wei.com>,
        <xiaoqian9@...wei.com>, <shaolexi@...wei.com>
Subject: [PATCH] semaphore: Add might_sleep() to down_*() family

Semaphore is sleeping lock. Add might_sleep() to down*() family
(with exception of down_trylock()) to detect atomic context sleep.

Previously discussed with Peter Zijlstra, see link:
 https://lore.kernel.org/lkml/20210806082320.GD22037@worktop.programming.kicks-ass.net

Signed-off-by: Xiaoming Ni <nixiaoming@...wei.com>
---
 kernel/locking/semaphore.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/locking/semaphore.c b/kernel/locking/semaphore.c
index 9aa855a96c4a..9ee381e4d2a4 100644
--- a/kernel/locking/semaphore.c
+++ b/kernel/locking/semaphore.c
@@ -54,6 +54,7 @@ void down(struct semaphore *sem)
 {
 	unsigned long flags;
 
+	might_sleep();
 	raw_spin_lock_irqsave(&sem->lock, flags);
 	if (likely(sem->count > 0))
 		sem->count--;
@@ -77,6 +78,7 @@ int down_interruptible(struct semaphore *sem)
 	unsigned long flags;
 	int result = 0;
 
+	might_sleep();
 	raw_spin_lock_irqsave(&sem->lock, flags);
 	if (likely(sem->count > 0))
 		sem->count--;
@@ -103,6 +105,7 @@ int down_killable(struct semaphore *sem)
 	unsigned long flags;
 	int result = 0;
 
+	might_sleep();
 	raw_spin_lock_irqsave(&sem->lock, flags);
 	if (likely(sem->count > 0))
 		sem->count--;
@@ -157,6 +160,7 @@ int down_timeout(struct semaphore *sem, long timeout)
 	unsigned long flags;
 	int result = 0;
 
+	might_sleep();
 	raw_spin_lock_irqsave(&sem->lock, flags);
 	if (likely(sem->count > 0))
 		sem->count--;
-- 
2.27.0