linux-kernel - [tip: locking/core] locking/mutex: Complain upon mutex API misuse in IRQ contexts

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Message-ID: <157242983900.29376.2332769194381838907.tip-bot2@tip-bot2>
Date:   Wed, 30 Oct 2019 10:03:59 -0000
From:   "tip-bot2 for Davidlohr Bueso" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Davidlohr Bueso <dbueso@...e.de>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>, dave@...olabs.net,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        linux-kernel@...r.kernel.org
Subject: [tip: locking/core] locking/mutex: Complain upon mutex API misuse in
 IRQ contexts

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

Commit-ID:     a0855d24fc22d49cdc25664fb224caee16998683
Gitweb:        https://git.kernel.org/tip/a0855d24fc22d49cdc25664fb224caee16998683
Author:        Davidlohr Bueso <dave@...olabs.net>
AuthorDate:    Thu, 24 Oct 2019 20:36:34 -07:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 29 Oct 2019 12:22:52 +01:00

locking/mutex: Complain upon mutex API misuse in IRQ contexts

Add warning checks if mutex_trylock() or mutex_unlock() are used in
IRQ contexts, under CONFIG_DEBUG_MUTEXES=y.

While the mutex rules and semantics are explicitly documented, this allows
to expose any abusers and robustifies the whole thing.

While trylock and unlock are non-blocking, calling from IRQ context
is still forbidden (lock must be within the same context as unlock).

Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: dave@...olabs.net
Link: https://lkml.kernel.org/r/20191025033634.3330-1-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/locking/mutex.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 5352ce5..54cc5f9 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -733,6 +733,9 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne
  */
 void __sched mutex_unlock(struct mutex *lock)
 {
+#ifdef CONFIG_DEBUG_MUTEXES
+	WARN_ON(in_interrupt());
+#endif
 #ifndef CONFIG_DEBUG_LOCK_ALLOC
 	if (__mutex_unlock_fast(lock))
 		return;
@@ -1413,6 +1416,7 @@ int __sched mutex_trylock(struct mutex *lock)
 
 #ifdef CONFIG_DEBUG_MUTEXES
 	DEBUG_LOCKS_WARN_ON(lock->magic != lock);
+	WARN_ON(in_interrupt());
 #endif
 
 	locked = __mutex_trylock(lock);