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 <[email protected]> --- 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
