TononixOS/ubports_kernel_google_msm
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

spinlock: lockbreak cleanup

Browse Source 
The break_lock data structure and code for spinlocks is quite nasty.
Not only does it double the size of a spinlock but it changes locking to
a potentially less optimal trylock.

Put all of that under CONFIG_GENERIC_LOCKBREAK, and introduce a
__raw_spin_is_contended that uses the lock data itself to determine whether
there are waiters on the lock, to be used if CONFIG_GENERIC_LOCKBREAK is
not set.

Rename need_lockbreak to spin_needbreak, make it use spin_is_contended to
decouple it from the spinlock implementation, and make it typesafe (rwlocks
do not have any need_lockbreak sites -- why do they even get bloated up
with that break_lock then?).

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Nick Piggin
2008-01-30 13:31:20 +01:00
committed by Ingo Molnar
parent a95d67f87e
commit 95c354fe9f
19 changed files with 72 additions and 37 deletions
Download Patch File Download Diff File Expand all files Collapse all files

21
include/linux/sched.h
View File

@@ -1922,23 +1922,16 @@ extern int cond_resched_softirq(void);
/*
* Does a critical section need to be broken due to another
* task waiting?:
* task waiting?: (technically does not depend on CONFIG_PREEMPT,
* but a general need for low latency)
*/
#if defined(CONFIG_PREEMPT) && defined(CONFIG_SMP)
# define need_lockbreak(lock) ((lock)->break_lock)
#else
# define need_lockbreak(lock) 0
#endif
/*
* Does a critical section need to be broken due to another
* task waiting or preemption being signalled:
*/
static inline int lock_need_resched(spinlock_t *lock)
static inline int spin_needbreak(spinlock_t *lock)
{
if (need_lockbreak(lock) || need_resched())
return 1;
#ifdef CONFIG_PREEMPT
return spin_is_contended(lock);
#else
return 0;
#endif
}
/*

6
include/linux/spinlock.h
View File

@@ -120,6 +120,12 @@ do { \
#define spin_is_locked(lock) __raw_spin_is_locked(&(lock)->raw_lock)
#ifdef CONFIG_GENERIC_LOCKBREAK
#define spin_is_contended(lock) ((lock)->break_lock)
#else
#define spin_is_contended(lock) __raw_spin_is_contended(&(lock)->raw_lock)
#endif
/**
* spin_unlock_wait - wait until the spinlock gets unlocked
* @lock: the spinlock in question.

4
include/linux/spinlock_types.h
View File

@@ -19,7 +19,7 @@
typedef struct {
raw_spinlock_t raw_lock;
#if defined(CONFIG_PREEMPT) && defined(CONFIG_SMP)
#ifdef CONFIG_GENERIC_LOCKBREAK
unsigned int break_lock;
#endif
#ifdef CONFIG_DEBUG_SPINLOCK
@@ -35,7 +35,7 @@ typedef struct {
typedef struct {
raw_rwlock_t raw_lock;
#if defined(CONFIG_PREEMPT) && defined(CONFIG_SMP)
#ifdef CONFIG_GENERIC_LOCKBREAK
unsigned int break_lock;
#endif
#ifdef CONFIG_DEBUG_SPINLOCK

2
include/linux/spinlock_up.h
View File

@@ -64,6 +64,8 @@ static inline void __raw_spin_unlock(raw_spinlock_t *lock)
# define __raw_spin_trylock(lock) ({ (void)(lock); 1; })
#endif /* DEBUG_SPINLOCK */
#define __raw_spin_is_contended(lock) (((void)(lock), 0))
#define __raw_read_can_lock(lock) (((void)(lock), 1))
#define __raw_write_can_lock(lock) (((void)(lock), 1))