From a12aa8a68dfef5de181f2e555aa950a0ab05411f Mon Sep 17 00:00:00 2001 From: David Lechner Date: Thu, 4 Jan 2018 19:46:08 -0600 Subject: clk: fix reentrancy of clk_enable() on UP systems 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 fixes the problem by skipping the call to spin_trylock_irqsave() on UP systems and relying solely on reference counting. We also make sure to set flags in this case so that we are not returning an uninitialized value. Suggested-by: Stephen Boyd Signed-off-by: David Lechner Signed-off-by: Stephen Boyd --- drivers/clk/clk.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'drivers/clk') diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 647d056df88c..b221d80cc7ba 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -141,10 +141,18 @@ static unsigned long clk_enable_lock(void) { unsigned long flags; - if (!spin_trylock_irqsave(&enable_lock, flags)) { + /* + * On UP systems, spin_trylock_irqsave() always returns true, even if + * we already hold the lock. So, in that case, we rely only on + * reference counting. + */ + if (!IS_ENABLED(CONFIG_SMP) || + !spin_trylock_irqsave(&enable_lock, flags)) { if (enable_owner == current) { enable_refcnt++; __acquire(enable_lock); + if (!IS_ENABLED(CONFIG_SMP)) + local_save_flags(flags); return flags; } spin_lock_irqsave(&enable_lock, flags); -- cgit v1.2.3