[PATCH] fix OProfile locking

This makes OProgile use get_task_mm() as discussed.  It also fixes up
Anton's previous patch.  Zwane's soaked this patch all night w/o
problems.

diff --git a/drivers/oprofile/buffer_sync.c b/drivers/oprofile/buffer_sync.c
index 2e1ab855d9434f0a207dcdc9c8196b05c38a95ae..884a532432436ba26c6a2a7f0c82c7af88673319 100644 (file)
--- a/drivers/oprofile/buffer_sync.c
+++ b/drivers/oprofile/buffer_sync.c
@@ -133,7 +133,7 @@ static struct notifier_block module_load_nb = {
  
 static void end_sync(void)
 {
-       end_cpu_timers();
+       end_cpu_work();
        /* make sure we don't leak task structs */
        process_task_mortuary();
        process_task_mortuary();
@@ -144,7 +144,7 @@ int sync_start(void)
 {
        int err;
 
-       start_cpu_timers();
+       start_cpu_work();
 
        err = task_handoff_register(&task_free_nb);
        if (err)
@@ -339,40 +339,25 @@ static void add_sample(struct mm_struct * mm, struct op_sample * s, int in_kerne
        }
 }
  
- 
+
 static void release_mm(struct mm_struct * mm)
 {
-       if (mm)
-               up_read(&mm->mmap_sem);
+       if (!mm)
+               return;
+       up_read(&mm->mmap_sem);
+       mmput(mm);
 }
 
 
-/* Take the task's mmap_sem to protect ourselves from
- * races when we do lookup_dcookie().
- */
 static struct mm_struct * take_tasks_mm(struct task_struct * task)
 {
-       struct mm_struct * mm;
-       
-       /* Subtle. We don't need to keep a reference to this task's mm,
-        * because, for the mm to be freed on another CPU, that would have
-        * to go through the task exit notifier, which ends up sleeping
-        * on the buffer_sem we hold, so we end up with mutual exclusion
-        * anyway.
-        */
-       task_lock(task);
-       mm = task->mm;
-       task_unlock(task);
- 
-       if (mm) {
-               /* needed to walk the task's VMAs */
+       struct mm_struct * mm = get_task_mm(task);
+       if (mm)
                down_read(&mm->mmap_sem);
-       }
- 
        return mm;
 }
- 
- 
+
+
 static inline int is_ctx_switch(unsigned long val)
 {
        return val == ~0UL;

diff --git a/drivers/oprofile/cpu_buffer.c b/drivers/oprofile/cpu_buffer.c
index 875badfe1cb80a83dc5983ba18c5d61e8b5504e4..420dc8e830a5391d300b3287dd3a9908366c985a 100644 (file)
--- a/drivers/oprofile/cpu_buffer.c
+++ b/drivers/oprofile/cpu_buffer.c
@@ -30,7 +30,7 @@ struct oprofile_cpu_buffer cpu_buffer[NR_CPUS] __cacheline_aligned;
 static void wq_sync_buffer(void *);
 
 #define DEFAULT_TIMER_EXPIRE (HZ / 10)
-int timers_enabled;
+int work_enabled;
 
 static void __free_cpu_buffers(int num)
 {
@@ -80,11 +80,11 @@ void free_cpu_buffers(void)
 }
 
 
-void start_cpu_timers(void)
+void start_cpu_work(void)
 {
        int i;
 
-       timers_enabled = 1;
+       work_enabled = 1;
 
        for_each_online_cpu(i) {
                struct oprofile_cpu_buffer * b = &cpu_buffer[i];
@@ -98,11 +98,11 @@ void start_cpu_timers(void)
 }
 
 
-void end_cpu_timers(void)
+void end_cpu_work(void)
 {
        int i;
 
-       timers_enabled = 0;
+       work_enabled = 0;
 
        for_each_online_cpu(i) {
                struct oprofile_cpu_buffer * b = &cpu_buffer[i];
@@ -220,6 +220,6 @@ static void wq_sync_buffer(void * data)
        sync_buffer(b->cpu);
 
        /* don't re-add the work if we're shutting down */
-       if (timers_enabled)
+       if (work_enabled)
                schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE);
 }

diff --git a/drivers/oprofile/cpu_buffer.h b/drivers/oprofile/cpu_buffer.h
index eeb494c3d62101e7a6f4c9381fa38e7f89f4e09a..23be2013a0c6dcd841d5ee994deb009c144e2066 100644 (file)
--- a/drivers/oprofile/cpu_buffer.h
+++ b/drivers/oprofile/cpu_buffer.h
@@ -20,8 +20,8 @@ struct task_struct;
 int alloc_cpu_buffers(void);
 void free_cpu_buffers(void);
 
-void start_cpu_timers(void);
-void end_cpu_timers(void);
+void start_cpu_work(void);
+void end_cpu_work(void);
 
 /* CPU buffer is composed of such entries (which are
  * also used for context switch notes)

diff --git a/kernel/fork.c b/kernel/fork.c
index ccd9ec7a786ef500fc19de4e65370d96944949bf..55ad085f064a79747acd5a58ed4cafd11604542b 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -483,6 +483,7 @@ void mmput(struct mm_struct *mm)
                mmdrop(mm);
        }
 }
+EXPORT_SYMBOL_GPL(mmput);
 
 /**
  * get_task_mm - acquire a reference to the task's mm
@@ -514,6 +515,7 @@ struct mm_struct *get_task_mm(struct task_struct *task)
        task_unlock(task);
        return mm;
 }
+EXPORT_SYMBOL_GPL(get_task_mm);
 
 /* Please note the differences between mmput and mm_release.
  * mmput is called whenever we stop holding onto a mm_struct,