| Message ID | 1515116768-17089-1-git-send-email-david@lechnology.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
On 01/04, David Lechner wrote: > 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> > --- Applied to clk-next
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 83c8df7..5add75b 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -143,10 +143,18 @@ 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);
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> --- v2 changes: * Use fix suggested by Stephen Boyd drivers/clk/clk.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)