[PATCH 1/2] locking/mutex: Move mutex flag macros to linux/mutex.h

[PATCH 1/2] locking/mutex: Move mutex flag macros to linux/mutex.h

[Mukesh Ojha]

There exist a place where we use hard code value for mutex
flag(e.g in mutex.h __mutex_owner()). Let's move the mutex
flag macros to header linux/mutex.h, so that it could be
reused at other places as well.

Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>
---
 include/linux/mutex.h  | 15 +++++++++++++++
 kernel/locking/mutex.c | 15 ---------------
 2 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index dcd03fe..79b28be 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -20,6 +20,21 @@
 #include <linux/osq_lock.h>
 #include <linux/debug_locks.h>
 
+/*
+ * @owner: contains: 'struct task_struct *' to the current lock owner,
+ * NULL means not owned. Since task_struct pointers are aligned at
+ * at least L1_CACHE_BYTES, we have low bits to store extra state.
+ *
+ * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup.
+ * Bit1 indicates unlock needs to hand the lock to the top-waiter
+ * Bit2 indicates handoff has been done and we're waiting for pickup.
+ */
+#define MUTEX_FLAG_WAITERS	0x01
+#define MUTEX_FLAG_HANDOFF	0x02
+#define MUTEX_FLAG_PICKUP	0x04
+
+#define MUTEX_FLAGS		0x07
+
 struct ww_acquire_ctx;
 
 /*
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 5e06973..b74c87d 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -50,21 +50,6 @@
 }
 EXPORT_SYMBOL(__mutex_init);
 
-/*
- * @owner: contains: 'struct task_struct *' to the current lock owner,
- * NULL means not owned. Since task_struct pointers are aligned at
- * at least L1_CACHE_BYTES, we have low bits to store extra state.
- *
- * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup.
- * Bit1 indicates unlock needs to hand the lock to the top-waiter
- * Bit2 indicates handoff has been done and we're waiting for pickup.
- */
-#define MUTEX_FLAG_WAITERS	0x01
-#define MUTEX_FLAG_HANDOFF	0x02
-#define MUTEX_FLAG_PICKUP	0x04
-
-#define MUTEX_FLAGS		0x07
-
 static inline struct task_struct *__owner_task(unsigned long owner)
 {
 	return (struct task_struct *)(owner & ~MUTEX_FLAGS);
-- 
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center,
Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project

[PATCH 2/2] locking/mutex: Use mutex flags macro instead of hard code value

[Mukesh Ojha]

Let's use the mutex flag macro(which got moved from mutex.c
to linux/mutex.h in the last patch) instead of hard code
value which was used in __mutex_owner().

Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>
---
 include/linux/mutex.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 79b28be..c3833ba 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -87,7 +87,7 @@ struct mutex {
  */
 static inline struct task_struct *__mutex_owner(struct mutex *lock)
 {
-	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
+	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
 }
 
 /*
-- 
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center,
Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project

Re: [PATCH 2/2] locking/mutex: Use mutex flags macro instead of hard code value

[Peter Zijlstra]

On Mon, Jul 29, 2019 at 04:22:58PM +0530, Mukesh Ojha wrote:
> Let's use the mutex flag macro(which got moved from mutex.c
> to linux/mutex.h in the last patch) instead of hard code
> value which was used in __mutex_owner().
> 
> Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>
> ---
>  include/linux/mutex.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> index 79b28be..c3833ba 100644
> --- a/include/linux/mutex.h
> +++ b/include/linux/mutex.h
> @@ -87,7 +87,7 @@ struct mutex {
>   */
>  static inline struct task_struct *__mutex_owner(struct mutex *lock)
>  {
> -	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
> +	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
>  }

I would _much_ rather move __mutex_owner() out of line, you're exposing
far too much stuff.

Re: [PATCH 2/2] locking/mutex: Use mutex flags macro instead of hard code value

[Mukesh Ojha]

On 7/29/2019 4:37 PM, Peter Zijlstra wrote:
> On Mon, Jul 29, 2019 at 04:22:58PM +0530, Mukesh Ojha wrote:
>> Let's use the mutex flag macro(which got moved from mutex.c
>> to linux/mutex.h in the last patch) instead of hard code
>> value which was used in __mutex_owner().
>>
>> Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>
>> ---
>>   include/linux/mutex.h | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
>> index 79b28be..c3833ba 100644
>> --- a/include/linux/mutex.h
>> +++ b/include/linux/mutex.h
>> @@ -87,7 +87,7 @@ struct mutex {
>>    */
>>   static inline struct task_struct *__mutex_owner(struct mutex *lock)
>>   {
>> -	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
>> +	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
>>   }
> I would _much_ rather move __mutex_owner() out of line, you're exposing
> far too much stuff.

if i understand you correctly, you want me to move __mutex_owner() to 
mutex.c
__mutex_owner() is used in mutex_is_locked() and mutex_trylock_recursive 
inside linux/mutex.h.

Shall i move them as well ?

Thanks,
Mukesh

Re: [PATCH 2/2] locking/mutex: Use mutex flags macro instead of hard code value

[Peter Zijlstra]

On Tue, Jul 30, 2019 at 01:23:13PM +0530, Mukesh Ojha wrote:
> 
> On 7/29/2019 4:37 PM, Peter Zijlstra wrote:
> > On Mon, Jul 29, 2019 at 04:22:58PM +0530, Mukesh Ojha wrote:
> > > Let's use the mutex flag macro(which got moved from mutex.c
> > > to linux/mutex.h in the last patch) instead of hard code
> > > value which was used in __mutex_owner().
> > > 
> > > Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>
> > > ---
> > >   include/linux/mutex.h | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> > > index 79b28be..c3833ba 100644
> > > --- a/include/linux/mutex.h
> > > +++ b/include/linux/mutex.h
> > > @@ -87,7 +87,7 @@ struct mutex {
> > >    */
> > >   static inline struct task_struct *__mutex_owner(struct mutex *lock)
> > >   {
> > > -	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
> > > +	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
> > >   }
> > I would _much_ rather move __mutex_owner() out of line, you're exposing
> > far too much stuff.
> 
> if i understand you correctly, you want me to move __mutex_owner() to
> mutex.c
> __mutex_owner() is used in mutex_is_locked() and mutex_trylock_recursive
> inside linux/mutex.h.
> 
> Shall i move them as well ?

Yes, then you can make __mutex_owner() static.

Thanks!

Re: [PATCH 2/2] locking/mutex: Use mutex flags macro instead of hard code value

[Mukesh Ojha]

On 7/30/2019 1:33 PM, Peter Zijlstra wrote:
> On Tue, Jul 30, 2019 at 01:23:13PM +0530, Mukesh Ojha wrote:
>> On 7/29/2019 4:37 PM, Peter Zijlstra wrote:
>>> On Mon, Jul 29, 2019 at 04:22:58PM +0530, Mukesh Ojha wrote:
>>>> Let's use the mutex flag macro(which got moved from mutex.c
>>>> to linux/mutex.h in the last patch) instead of hard code
>>>> value which was used in __mutex_owner().
>>>>
>>>> Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>
>>>> ---
>>>>    include/linux/mutex.h | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
>>>> index 79b28be..c3833ba 100644
>>>> --- a/include/linux/mutex.h
>>>> +++ b/include/linux/mutex.h
>>>> @@ -87,7 +87,7 @@ struct mutex {
>>>>     */
>>>>    static inline struct task_struct *__mutex_owner(struct mutex *lock)
>>>>    {
>>>> -	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
>>>> +	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
>>>>    }
>>> I would _much_ rather move __mutex_owner() out of line, you're exposing
>>> far too much stuff.
>> if i understand you correctly, you want me to move __mutex_owner() to
>> mutex.c
>> __mutex_owner() is used in mutex_is_locked() and mutex_trylock_recursive
>> inside linux/mutex.h.
>>
>> Shall i move them as well ?
> Yes, then you can make __mutex_owner() static.

To make it static , i have to export mutex_is_locked() after moving it 
inside mutex.c, so that other module can use it.

Also are we thinking of removing
static inline /* __deprecated */ __must_check enum 
mutex_trylock_recursive_enum
mutex_trylock_recursive(struct mutex *lock)

inside linux/mutex.h in future ?

As i see it is used at one or two places and there is a check inside 
checkpatch guarding its further use .

Thanks,
Mukesh


>
> Thanks!

Re: [PATCH 2/2] locking/mutex: Use mutex flags macro instead of hard code value

[Peter Zijlstra]

On Tue, Jul 30, 2019 at 06:10:49PM +0530, Mukesh Ojha wrote:

> To make it static , i have to export mutex_is_locked() after moving it
> inside mutex.c, so that other module can use it.

Yep, see below -- completely untested.

> Also are we thinking of removing
> static inline /* __deprecated */ __must_check enum
> mutex_trylock_recursive_enum
> mutex_trylock_recursive(struct mutex *lock)
> 
> inside linux/mutex.h in future ?
> 
> As i see it is used at one or two places and there is a check inside
> checkpatch guarding its further use .

That was the idea; recursive locking is evil, but we have these two
legacy sites.

---

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index dcd03fee6e01..eb8c62aba263 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -65,29 +65,6 @@ struct mutex {
 #endif
 };
 
-/*
- * Internal helper function; C doesn't allow us to hide it :/
- *
- * DO NOT USE (outside of mutex code).
- */
-static inline struct task_struct *__mutex_owner(struct mutex *lock)
-{
-	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
-}
-
-/*
- * This is the control structure for tasks blocked on mutex,
- * which resides on the blocked task's kernel stack:
- */
-struct mutex_waiter {
-	struct list_head	list;
-	struct task_struct	*task;
-	struct ww_acquire_ctx	*ww_ctx;
-#ifdef CONFIG_DEBUG_MUTEXES
-	void			*magic;
-#endif
-};
-
 #ifdef CONFIG_DEBUG_MUTEXES
 
 #define __DEBUG_MUTEX_INITIALIZER(lockname)				\
@@ -144,10 +121,7 @@ extern void __mutex_init(struct mutex *lock, const char *name,
  *
  * Returns true if the mutex is locked, false if unlocked.
  */
-static inline bool mutex_is_locked(struct mutex *lock)
-{
-	return __mutex_owner(lock) != NULL;
-}
+extern bool mutex_is_locked(struct mutex *lock);
 
 /*
  * See kernel/locking/mutex.c for detailed documentation of these APIs.
@@ -220,13 +194,7 @@ enum mutex_trylock_recursive_enum {
  *  - MUTEX_TRYLOCK_SUCCESS   - lock acquired,
  *  - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
  */
-static inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
-mutex_trylock_recursive(struct mutex *lock)
-{
-	if (unlikely(__mutex_owner(lock) == current))
-		return MUTEX_TRYLOCK_RECURSIVE;
-
-	return mutex_trylock(lock);
-}
+extern /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
+mutex_trylock_recursive(struct mutex *lock);
 
 #endif /* __LINUX_MUTEX_H */
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 5e069734363c..2f73935a6053 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -36,6 +36,19 @@
 # include "mutex.h"
 #endif
 
+/*
+ * This is the control structure for tasks blocked on mutex,
+ * which resides on the blocked task's kernel stack:
+ */
+struct mutex_waiter {
+	struct list_head	list;
+	struct task_struct	*task;
+	struct ww_acquire_ctx	*ww_ctx;
+#ifdef CONFIG_DEBUG_MUTEXES
+	void			*magic;
+#endif
+};
+
 void
 __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
 {
@@ -65,6 +78,16 @@ EXPORT_SYMBOL(__mutex_init);
 
 #define MUTEX_FLAGS		0x07
 
+/*
+ * Internal helper function; C doesn't allow us to hide it :/
+ *
+ * DO NOT USE (outside of mutex code).
+ */
+static inline struct task_struct *__mutex_owner(struct mutex *lock)
+{
+	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
+}
+
 static inline struct task_struct *__owner_task(unsigned long owner)
 {
 	return (struct task_struct *)(owner & ~MUTEX_FLAGS);
@@ -75,6 +98,22 @@ static inline unsigned long __owner_flags(unsigned long owner)
 	return owner & MUTEX_FLAGS;
 }
 
+bool mutex_is_locked(struct mutex *lock)
+{
+	return __mutex_owner(lock) != NULL;
+}
+EXPORT_SYMBOL(mutex_is_locked);
+
+__must_check enum mutex_trylock_recursive_enum
+mutex_trylock_recursive(struct mutex *lock)
+{
+	if (unlikely(__mutex_owner(lock) == current))
+		return MUTEX_TRYLOCK_RECURSIVE;
+
+	return mutex_trylock(lock);
+}
+EXPORT_SYMBOL(mutex_trylock_recursive);
+
 /*
  * Trylock variant that retuns the owning task on failure.
  */

Re: [PATCH 2/2] locking/mutex: Use mutex flags macro instead of hard code value

[Mukesh Ojha]

On 7/30/2019 9:32 PM, Peter Zijlstra wrote:
> On Tue, Jul 30, 2019 at 06:10:49PM +0530, Mukesh Ojha wrote:
>
>> To make it static , i have to export mutex_is_locked() after moving it
>> inside mutex.c, so that other module can use it.
> Yep, see below -- completely untested.
>
>> Also are we thinking of removing
>> static inline /* __deprecated */ __must_check enum
>> mutex_trylock_recursive_enum
>> mutex_trylock_recursive(struct mutex *lock)
>>
>> inside linux/mutex.h in future ?
>>
>> As i see it is used at one or two places and there is a check inside
>> checkpatch guarding its further use .
> That was the idea; recursive locking is evil, but we have these two
> legacy sites.
>
> ---
>
> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> index dcd03fee6e01..eb8c62aba263 100644
> --- a/include/linux/mutex.h
> +++ b/include/linux/mutex.h
> @@ -65,29 +65,6 @@ struct mutex {
>   #endif
>   };
>   
> -/*
> - * Internal helper function; C doesn't allow us to hide it :/
> - *
> - * DO NOT USE (outside of mutex code).
> - */
> -static inline struct task_struct *__mutex_owner(struct mutex *lock)
> -{
> -	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
> -}
> -
> -/*
> - * This is the control structure for tasks blocked on mutex,
> - * which resides on the blocked task's kernel stack:
> - */
> -struct mutex_waiter {
> -	struct list_head	list;
> -	struct task_struct	*task;
> -	struct ww_acquire_ctx	*ww_ctx;
> -#ifdef CONFIG_DEBUG_MUTEXES
> -	void			*magic;
> -#endif
> -};
> -
>   #ifdef CONFIG_DEBUG_MUTEXES
>   
>   #define __DEBUG_MUTEX_INITIALIZER(lockname)				\
> @@ -144,10 +121,7 @@ extern void __mutex_init(struct mutex *lock, const char *name,
>    *
>    * Returns true if the mutex is locked, false if unlocked.
>    */
> -static inline bool mutex_is_locked(struct mutex *lock)
> -{
> -	return __mutex_owner(lock) != NULL;
> -}
> +extern bool mutex_is_locked(struct mutex *lock);
>   
>   /*
>    * See kernel/locking/mutex.c for detailed documentation of these APIs.
> @@ -220,13 +194,7 @@ enum mutex_trylock_recursive_enum {
>    *  - MUTEX_TRYLOCK_SUCCESS   - lock acquired,
>    *  - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
>    */
> -static inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
> -mutex_trylock_recursive(struct mutex *lock)
> -{
> -	if (unlikely(__mutex_owner(lock) == current))
> -		return MUTEX_TRYLOCK_RECURSIVE;
> -
> -	return mutex_trylock(lock);
> -}
> +extern /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
> +mutex_trylock_recursive(struct mutex *lock);
>   
>   #endif /* __LINUX_MUTEX_H */
> diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
> index 5e069734363c..2f73935a6053 100644
> --- a/kernel/locking/mutex.c
> +++ b/kernel/locking/mutex.c
> @@ -36,6 +36,19 @@
>   # include "mutex.h"
>   #endif
>   
> +/*
> + * This is the control structure for tasks blocked on mutex,
> + * which resides on the blocked task's kernel stack:
> + */
> +struct mutex_waiter {
> +	struct list_head	list;
> +	struct task_struct	*task;
> +	struct ww_acquire_ctx	*ww_ctx;
> +#ifdef CONFIG_DEBUG_MUTEXES
> +	void			*magic;
> +#endif
> +};

i already did in v2  except this above waiter struct, will do it in v3.

Cheers,

Mukesh

> +
>   void
>   __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
>   {
> @@ -65,6 +78,16 @@ EXPORT_SYMBOL(__mutex_init);
>   
>   #define MUTEX_FLAGS		0x07
>   
> +/*
> + * Internal helper function; C doesn't allow us to hide it :/
> + *
> + * DO NOT USE (outside of mutex code).
> + */
> +static inline struct task_struct *__mutex_owner(struct mutex *lock)
> +{
> +	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
> +}
> +
>   static inline struct task_struct *__owner_task(unsigned long owner)
>   {
>   	return (struct task_struct *)(owner & ~MUTEX_FLAGS);
> @@ -75,6 +98,22 @@ static inline unsigned long __owner_flags(unsigned long owner)
>   	return owner & MUTEX_FLAGS;
>   }
>   
> +bool mutex_is_locked(struct mutex *lock)
> +{
> +	return __mutex_owner(lock) != NULL;
> +}
> +EXPORT_SYMBOL(mutex_is_locked);
> +
> +__must_check enum mutex_trylock_recursive_enum
> +mutex_trylock_recursive(struct mutex *lock)
> +{
> +	if (unlikely(__mutex_owner(lock) == current))
> +		return MUTEX_TRYLOCK_RECURSIVE;
> +
> +	return mutex_trylock(lock);
> +}
> +EXPORT_SYMBOL(mutex_trylock_recursive);
> +
>   /*
>    * Trylock variant that retuns the owning task on failure.
>    */

[PATCH 1/2 v2] locking/mutex: Make __mutex_owner static to mutex.c

[Mukesh Ojha]

__mutex_owner() should only be used by the mutex api's.
So, put this restiction let's move the __mutex_owner()
function definition from linux/mutex.h to mutex.c file.

There exist functions that uses __mutex_owner() like
mutex_is_locked() and mutex_trylock_recursive(), So
to keep the thing intact move them as well and
export them.

Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>
---
Changes in v2:
- On Peterz suggestion, moved __mutex_owner() to mutex.c to
  make it static to mutex.c.

- Exported mutex_is_owner() and mutex_trylock_recursive()
  to keep the existing thing intact as there are loadable
  modules which uses these functions.

 include/linux/mutex.h  | 44 +++-----------------------------------------
 kernel/locking/mutex.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 41 deletions(-)

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index dcd03fe..841b47d 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -66,16 +66,6 @@ struct mutex {
 };
 
 /*
- * Internal helper function; C doesn't allow us to hide it :/
- *
- * DO NOT USE (outside of mutex code).
- */
-static inline struct task_struct *__mutex_owner(struct mutex *lock)
-{
-	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
-}
-
-/*
  * This is the control structure for tasks blocked on mutex,
  * which resides on the blocked task's kernel stack:
  */
@@ -138,17 +128,10 @@ static inline void mutex_destroy(struct mutex *lock) {}
 extern void __mutex_init(struct mutex *lock, const char *name,
 			 struct lock_class_key *key);
 
-/**
- * mutex_is_locked - is the mutex locked
- * @lock: the mutex to be queried
- *
- * Returns true if the mutex is locked, false if unlocked.
- */
-static inline bool mutex_is_locked(struct mutex *lock)
-{
-	return __mutex_owner(lock) != NULL;
-}
+extern inline bool mutex_is_locked(struct mutex *lock);
 
+extern inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
+mutex_trylock_recursive(struct mutex *lock);
 /*
  * See kernel/locking/mutex.c for detailed documentation of these APIs.
  * Also see Documentation/locking/mutex-design.rst.
@@ -208,25 +191,4 @@ enum mutex_trylock_recursive_enum {
 	MUTEX_TRYLOCK_RECURSIVE,
 };
 
-/**
- * mutex_trylock_recursive - trylock variant that allows recursive locking
- * @lock: mutex to be locked
- *
- * This function should not be used, _ever_. It is purely for hysterical GEM
- * raisins, and once those are gone this will be removed.
- *
- * Returns:
- *  - MUTEX_TRYLOCK_FAILED    - trylock failed,
- *  - MUTEX_TRYLOCK_SUCCESS   - lock acquired,
- *  - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
- */
-static inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
-mutex_trylock_recursive(struct mutex *lock)
-{
-	if (unlikely(__mutex_owner(lock) == current))
-		return MUTEX_TRYLOCK_RECURSIVE;
-
-	return mutex_trylock(lock);
-}
-
 #endif /* __LINUX_MUTEX_H */
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 5e06973..f73250a 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -65,6 +65,50 @@
 
 #define MUTEX_FLAGS		0x07
 
+/*
+ * Internal helper function; C doesn't allow us to hide it :/
+ *
+ * DO NOT USE (outside of mutex code).
+ */
+static inline struct task_struct *__mutex_owner(struct mutex *lock)
+{
+	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
+}
+
+/**
+ * mutex_is_locked - is the mutex locked
+ * @lock: the mutex to be queried
+ *
+ * Returns true if the mutex is locked, false if unlocked.
+ */
+inline bool mutex_is_locked(struct mutex *lock)
+{
+	return __mutex_owner(lock) != NULL;
+}
+EXPORT_SYMBOL(mutex_is_locked);
+
+/**
+ * mutex_trylock_recursive - trylock variant that allows recursive locking
+ * @lock: mutex to be locked
+ *
+ * This function should not be used, _ever_. It is purely for hysterical GEM
+ * raisins, and once those are gone this will be removed.
+ *
+ * Returns:
+ *  - MUTEX_TRYLOCK_FAILED    - trylock failed,
+ *  - MUTEX_TRYLOCK_SUCCESS   - lock acquired,
+ *  - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
+ */
+inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
+mutex_trylock_recursive(struct mutex *lock)
+{
+	if (unlikely(__mutex_owner(lock) == current))
+		return MUTEX_TRYLOCK_RECURSIVE;
+
+	return mutex_trylock(lock);
+}
+EXPORT_SYMBOL(mutex_trylock_recursive);
+
 static inline struct task_struct *__owner_task(unsigned long owner)
 {
 	return (struct task_struct *)(owner & ~MUTEX_FLAGS);
-- 
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center,
Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project

[PATCH 2/2 v2] locking/mutex: Use mutex flags macro instead of hard code value

[Mukesh Ojha]

Use the mutex flag macro instead of hard code value inside
__mutex_owner().

Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>
---
Changes in v2:
 - Framed the commit according the changes done in 1/2 of
   the patchset.

 kernel/locking/mutex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index f73250a..1c8f86a 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -72,7 +72,7 @@
  */
 static inline struct task_struct *__mutex_owner(struct mutex *lock)
 {
-	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
+	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
 }
 
 /**
-- 
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center,
Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project