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Message-Id: <20220630135934.1799248-2-aahringo@redhat.com>
Date: Thu, 30 Jun 2022 09:59:33 -0400
From: Alexander Aring <aahringo@...hat.com>
To: will@...nel.org
Cc: peterz@...radead.org, boqun.feng@...il.com, mark.rutland@....com,
thunder.leizhen@...wei.com, jacob.e.keller@...el.com,
akpm@...ux-foundation.org, linux-sparse@...r.kernel.org,
cluster-devel@...hat.com, luc.vanoostenryck@...il.com,
torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
aahringo@...hat.com
Subject: [RFC 1/2] refcount: add __cond_lock() for conditional lock refcount API
This patch adds the __cond_lock() macro to refcounts conditional lock
API. Currently sparse cannot detect the conditional lock handling of
refcount_dec_and_lock() functionality and prints a context imbalance
warning like:
warning: context imbalance in 'put_rsb' - unexpected unlock
with this patch and having the refcount_dec_and_lock() functionality
inside the if condition to decide whenever doing unlock or not the
warning disappears.
The patch follows a similar naming scheme like raw_spin_trylock() by
adding a "raw_" prefix to refcount_dec_and_lock() functionality and
introduce a macro for the replaced functions that uses __cond_lock()
to signal that an acquire depends on the return value of the passed
function.
A cast to bool seems to be necessary because __cond_lock() does return a
non-boolean scalar type.
The __must_check annotation was tested and is still working with this
patch applied.
Signed-off-by: Alexander Aring <aahringo@...hat.com>
---
include/linux/refcount.h | 21 ++++++++++++++++-----
lib/refcount.c | 23 ++++++++++++-----------
2 files changed, 28 insertions(+), 16 deletions(-)
diff --git a/include/linux/refcount.h b/include/linux/refcount.h
index b8a6e387f8f9..be7b970ce475 100644
--- a/include/linux/refcount.h
+++ b/include/linux/refcount.h
@@ -361,9 +361,20 @@ static inline void refcount_dec(refcount_t *r)
extern __must_check bool refcount_dec_if_one(refcount_t *r);
extern __must_check bool refcount_dec_not_one(refcount_t *r);
-extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock);
-extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock);
-extern __must_check bool refcount_dec_and_lock_irqsave(refcount_t *r,
- spinlock_t *lock,
- unsigned long *flags);
+extern __must_check bool raw_refcount_dec_and_mutex_lock(refcount_t *r,
+ struct mutex *lock);
+#define refcount_dec_and_mutex_lock(r, lock) \
+ ((bool)(__cond_lock(lock, raw_refcount_dec_and_mutex_lock(r, lock))))
+
+extern __must_check bool raw_refcount_dec_and_lock(refcount_t *r,
+ spinlock_t *lock);
+#define refcount_dec_and_lock(r, lock) \
+ ((bool)(__cond_lock(lock, raw_refcount_dec_and_lock(r, lock))))
+
+extern __must_check bool raw_refcount_dec_and_lock_irqsave(refcount_t *r,
+ spinlock_t *lock,
+ unsigned long *flags);
+#define refcount_dec_and_lock_irqsave(r, lock, flags) \
+ ((bool)(__cond_lock(lock, raw_refcount_dec_and_lock_irqsave(r, lock, flags))))
+
#endif /* _LINUX_REFCOUNT_H */
diff --git a/lib/refcount.c b/lib/refcount.c
index a207a8f22b3c..1a8c7b9aba23 100644
--- a/lib/refcount.c
+++ b/lib/refcount.c
@@ -110,7 +110,7 @@ EXPORT_SYMBOL(refcount_dec_not_one);
* Return: true and hold mutex if able to decrement refcount to 0, false
* otherwise
*/
-bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock)
+bool raw_refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock)
{
if (refcount_dec_not_one(r))
return false;
@@ -123,11 +123,11 @@ bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock)
return true;
}
-EXPORT_SYMBOL(refcount_dec_and_mutex_lock);
+EXPORT_SYMBOL(raw_refcount_dec_and_mutex_lock);
/**
- * refcount_dec_and_lock - return holding spinlock if able to decrement
- * refcount to 0
+ * raw_refcount_dec_and_lock - return holding spinlock if able to decrement
+ * refcount to 0
* @r: the refcount
* @lock: the spinlock to be locked
*
@@ -141,7 +141,7 @@ EXPORT_SYMBOL(refcount_dec_and_mutex_lock);
* Return: true and hold spinlock if able to decrement refcount to 0, false
* otherwise
*/
-bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
+bool raw_refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
{
if (refcount_dec_not_one(r))
return false;
@@ -154,11 +154,12 @@ bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
return true;
}
-EXPORT_SYMBOL(refcount_dec_and_lock);
+EXPORT_SYMBOL(raw_refcount_dec_and_lock);
/**
- * refcount_dec_and_lock_irqsave - return holding spinlock with disabled
- * interrupts if able to decrement refcount to 0
+ * raw_refcount_dec_and_lock_irqsave - return holding spinlock with disabled
+ * interrupts if able to decrement
+ * refcount to 0
* @r: the refcount
* @lock: the spinlock to be locked
* @flags: saved IRQ-flags if the is acquired
@@ -169,8 +170,8 @@ EXPORT_SYMBOL(refcount_dec_and_lock);
* Return: true and hold spinlock if able to decrement refcount to 0, false
* otherwise
*/
-bool refcount_dec_and_lock_irqsave(refcount_t *r, spinlock_t *lock,
- unsigned long *flags)
+bool raw_refcount_dec_and_lock_irqsave(refcount_t *r, spinlock_t *lock,
+ unsigned long *flags)
{
if (refcount_dec_not_one(r))
return false;
@@ -183,4 +184,4 @@ bool refcount_dec_and_lock_irqsave(refcount_t *r, spinlock_t *lock,
return true;
}
-EXPORT_SYMBOL(refcount_dec_and_lock_irqsave);
+EXPORT_SYMBOL(raw_refcount_dec_and_lock_irqsave);
--
2.31.1
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