On Fri, 2012-03-02 at 16:20 +0100, Thomas Gleixner wrote:
> Already queued. I'd say #4 is a bug fix as well, though I
> fundamentally hate the ass backwards semantics of that new function.
It is a bug fix, but I don't like it either. Note, that the patch didn't
update the pin_current_cpu() code, which would have to be done too (to
be a full fix).
But I was also thinking that as a work around, as we plan on changing
this code anyway. Instead of adding a new API which is ass backwards,
just encompass the cpu_hotplug.lock instead. Something like this:
Not tested nor complied.
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Yes this is ugly, but at least we don't introduce an ass backwards
semantic.
diff --git a/kernel/cpu.c b/kernel/cpu.c
index fa40834..c25b5ff 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -46,7 +46,12 @@ static int cpu_hotplug_disabled;
static struct {
struct task_struct *active_writer;
+#ifdef CONFIG_PREEMPT_RT_FULL
+ /* Makes the lock keep the task's state */
+ spinlock_t lock;
+#else
struct mutex lock; /* Synchronizes accesses to refcount, */
+#endif
/*
* Also blocks the new readers during
* an ongoing cpu hotplug operation.
@@ -58,6 +63,14 @@ static struct {
.refcount = 0,
};
+#ifdef CONFIG_PREEMPT_RT_FULL
+# define hotplug_lock() spin_lock(&cpu_hotplug.lock)
+# define hotplug_unlock() spin_unlock(&cpu_hotplug.lock)
+#else
+# define hotplug_lock() mutex_lock(&cpu_hotplug.lock)
+# define hotplug_lock() mutex_unlock(&cpu_hotplug.lock)
+#endif
+
struct hotplug_pcp {
struct task_struct *unplug;
int refcount;
@@ -87,8 +100,8 @@ retry:
return;
}
preempt_enable();
- mutex_lock(&cpu_hotplug.lock);
- mutex_unlock(&cpu_hotplug.lock);
+ hotplug_lock();
+ hotplug_unlock();
preempt_disable();
goto retry;
}
@@ -161,9 +174,9 @@ void get_online_cpus(void)
might_sleep();
if (cpu_hotplug.active_writer == current)
return;
- mutex_lock(&cpu_hotplug.lock);
+ hotplug_lock();
cpu_hotplug.refcount++;
- mutex_unlock(&cpu_hotplug.lock);
+ hotplug_unlock();
}
EXPORT_SYMBOL_GPL(get_online_cpus);
@@ -172,10 +185,10 @@ void put_online_cpus(void)
{
if (cpu_hotplug.active_writer == current)
return;
- mutex_lock(&cpu_hotplug.lock);
+ hotplug_lock();
if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
wake_up_process(cpu_hotplug.active_writer);
- mutex_unlock(&cpu_hotplug.lock);
+ hotplug_unlock();
}
EXPORT_SYMBOL_GPL(put_online_cpus);
@@ -207,11 +220,11 @@ static void cpu_hotplug_begin(void)
cpu_hotplug.active_writer = current;
for (;;) {
- mutex_lock(&cpu_hotplug.lock);
+ hotplug_lock();
if (likely(!cpu_hotplug.refcount))
break;
__set_current_state(TASK_UNINTERRUPTIBLE);
- mutex_unlock(&cpu_hotplug.lock);
+ hotplug_unlock();
schedule();
}
}
@@ -219,7 +232,7 @@ static void cpu_hotplug_begin(void)
static void cpu_hotplug_done(void)
{
cpu_hotplug.active_writer = NULL;
- mutex_unlock(&cpu_hotplug.lock);
+ hotplug_unlock();
}
#else /* #if CONFIG_HOTPLUG_CPU */
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