From: David Lechner david@lechnology.com
[ Upstream commit a12aa8a68dfef5de181f2e555aa950a0ab05411f ]
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 Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- drivers/clk/clk.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index f13c3f4228d4..a20538c4c2fa 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -119,10 +119,18 @@ 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);