[PATCH] clk: fix reentrancy of clk_enable() on UP systems
From: David Lechner
Date: Tue Dec 26 2017 - 12:24:39 EST
Reentrant calls to clk_enable() are not working on UP systems. This is
caused by the fact spin_trylock_irqsave() always returns true when
CONFIG_SMP=n (and CONFIG_DEBUG_SPINLOCK=n) which causes the reference
counting to not work correctly when clk_enable_lock() is called twice
before clk_enable_unlock() is called (this happens when clk_enable()
is called from within another clk_enable()).
This introduces a new set of clk_enable_lock() and clk_enable_unlock()
functions for UP systems that doesn't use spinlocks but effectively does
the same thing as the SMP version of the functions.
Signed-off-by: David Lechner <david@xxxxxxxxxxxxxx>
---
Previous discussion of this issue for reference:
* https://patchwork.kernel.org/patch/10108437/
* https://patchwork.kernel.org/patch/10115483/
drivers/clk/clk.c | 39 +++++++++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index bb1b1f9..259a77f 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -136,6 +136,8 @@ static void clk_prepare_unlock(void)
mutex_unlock(&prepare_lock);
}
+#ifdef CONFIG_SMP
+
static unsigned long clk_enable_lock(void)
__acquires(enable_lock)
{
@@ -170,6 +172,43 @@ static void clk_enable_unlock(unsigned long flags)
spin_unlock_irqrestore(&enable_lock, flags);
}
+#else
+
+static unsigned long clk_enable_lock(void)
+ __acquires(enable_lock)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ preempt_disable();
+ __acquire(enable_lock);
+
+ if (enable_refcnt++ == 0) {
+ WARN_ON_ONCE(enable_owner != NULL);
+ enable_owner = current;
+ } else {
+ WARN_ON_ONCE(enable_owner != current);
+ }
+
+ return flags;
+}
+
+static void clk_enable_unlock(unsigned long flags)
+ __releases(enable_lock)
+{
+ WARN_ON_ONCE(enable_owner != current);
+ WARN_ON_ONCE(enable_refcnt == 0);
+
+ if (--enable_refcnt == 0)
+ enable_owner = NULL;
+
+ __release(enable_lock);
+ local_irq_restore(flags);
+ preempt_enable();
+}
+
+#endif
+
static bool clk_core_is_prepared(struct clk_core *core)
{
bool ret = false;
--
2.7.4