[RFC 7/7] Add Markers Into Semaphore Primitives

Mathieu Desnoyers
2007-11-13T19:43:25Z

[-- Attachment #1: add-markers-into-semaphore-primitives.patch --]
[-- Type: text/plain, Size: 3111 bytes --]

This patch adds several markers around semaphore primitives.
Along with a tracing application this patch can be useful for measuring
kernel semaphore usage and contention.

Signed-off-by: Mike Mason <mmlnx@us.ibm.com>
Signed-off-by: David Wilder <dwilder@us.ibm.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---
lib/semaphore-sleepers.c | 9 +++++++++
1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/lib/semaphore-sleepers.c b/lib/semaphore-sleepers.c
index 1281805..5343a96 100644
--- a/lib/semaphore-sleepers.c
+++ b/lib/semaphore-sleepers.c
@@ -15,6 +15,7 @@
#include <linux/sched.h>
#include <linux/err.h>
#include <linux/init.h>
+#include <linux/marker.h>
#include <asm/semaphore.h>

/*
@@ -50,6 +51,7 @@

fastcall void __up(struct semaphore *sem)
{
+ trace_mark(sem_up, "%p", sem);
wake_up(&sem->wait);
}

@@ -59,6 +61,7 @@ fastcall void __sched __down(struct semaphore * sem)
DECLARE_WAITQUEUE(wait, tsk);
unsigned long flags;

+ trace_mark(sem_down, "%p", sem);
tsk->state = TASK_UNINTERRUPTIBLE;
spin_lock_irqsave(&sem->wait.lock, flags);
add_wait_queue_exclusive_locked(&sem->wait, &wait);
@@ -73,12 +76,14 @@ fastcall void __sched __down(struct semaphore * sem)
* the wait_queue_head.
*/
if (!atomic_add_negative(sleepers - 1, &sem->count)) {
+ trace_mark(sem_down_resume, "%p", sem);
sem->sleepers = 0;
break;
}
sem->sleepers = 1; /* us - see -1 above */
spin_unlock_irqrestore(&sem->wait.lock, flags);

+ trace_mark(sem_down_sched, "%p", sem);
schedule();

spin_lock_irqsave(&sem->wait.lock, flags);
@@ -97,6 +102,7 @@ fastcall int __sched __down_interruptible(struct semaphore * sem)
DECLARE_WAITQUEUE(wait, tsk);
unsigned long flags;

+ trace_mark(sem_down_intr, "%p", sem);
tsk->state = TASK_INTERRUPTIBLE;
spin_lock_irqsave(&sem->wait.lock, flags);
add_wait_queue_exclusive_locked(&sem->wait, &wait);
@@ -113,6 +119,7 @@ fastcall int __sched __down_interruptible(struct semaphore * sem)
* and exit.
*/
if (signal_pending(current)) {
+ trace_mark(sem_down_intr_fail, "%p", sem);
retval = -EINTR;
sem->sleepers = 0;
atomic_add(sleepers, &sem->count);
@@ -126,12 +133,14 @@ fastcall int __sched __down_interruptible(struct semaphore * sem)
* still hoping to get the semaphore.
*/
if (!atomic_add_negative(sleepers - 1, &sem->count)) {
+ trace_mark(sem_down_intr_resume, "%p", sem);
sem->sleepers = 0;
break;
}
sem->sleepers = 1; /* us - see -1 above */
spin_unlock_irqrestore(&sem->wait.lock, flags);

+ trace_mark(sem_down_intr_sched, "%p", sem);
schedule();

spin_lock_irqsave(&sem->wait.lock, flags);

-
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