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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>
hifive-unleashed-5.1
David Lechner 2018-01-04 19:46:08 -06:00 committed by Stephen Boyd
parent 4fbd8d194f
commit a12aa8a68d
1 changed files with 9 additions and 1 deletions
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10
drivers/clk/clk.c
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@ -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);