Commit a12aa8a6 authored Jan 04, 2018 by David Lechner Committed by Stephen Boyd Jan 10, 2018

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 <sboyd@codeaurora.org>
Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

parent 4fbd8d19

drivers/clk/clk.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -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);