On Fri, 9 Apr 2010, Michal Nazarewicz wrote:
> New wait_event_interruptible{,_exclusive}_locked{,_irq,_irqsave}
> macros added. They work just like versions without _locked* suffix
The _irqsave variant is really not necessary. It's actively wrong.
If you go to wait then the state _before_ acquiring the waitqueue head
lock must be irqs enabled. Otherwise you would schedule with
interrupts disabled after the unlock_irqrestore which is a BUG.
So if there is code which uses spin_lock_irqsave() in the wait path
then this code is wrong and needs to be fixed to spin_(un)lock_irq()
first instead of adding a bogus interface.
> +
> +#define __wait_event_interruptible_locked(wq, condition, ret, exclusive, lock, unlock, lock_args) \
That will also simplify this to (wq, condition, exclusive, lockmode)
> +do { \
> + DEFINE_WAIT(__wait); \
> + \
> + if (exclusive) \
> + __wait.flags |= WQ_FLAG_EXCLUSIVE; \
> + else \
> + __wait.flags &= ~WQ_FLAG_EXCLUSIVE; \
> + __add_wait_queue_tail(&(wq), &__wait); \
> + \
> + do { \
> + set_current_state(TASK_INTERRUPTIBLE); \
> + if (signal_pending(current)) { \
> + ret = -ERESTARTSYS; \
> + break; \
> + } \
> + spin_unlock ##unlock lock_args; \
> + schedule(); \
> + spin_lock ##lock lock_args; \
> + } while (!(condition)); \
> + __remove_wait_queue(&(wq), &__wait); \
> + __set_current_state(TASK_RUNNING); \
> +} while (0)
> +
> +
> +/**
> + * wait_event_interruptible_locked - sleep until a condition gets true
> + * @wq: the waitqueue to wait on
> + * @condition: a C expression for the event to wait for
> + *
> + * The process is put to sleep (TASK_INTERRUPTIBLE) until the
> + * @condition evaluates to true or a signal is received.
> + * The @condition is checked each time the waitqueue @wq is woken up.
> + *
> + * It must be called with wq.lock being held. This spinlock is
> + * unlocked while sleeping but @condition testing is done while lock
> + * is held and when this macro exits the lock is held.
> + *
> + * The lock is locked/unlocked using spin_lock()/spin_unlock()
> + * functions which must match the way they are locked/unlocked outside
> + * of this macro.
> + *
> + * wake_up_locked() has to be called after changing any variable that could
> + * change the result of the wait condition.
> + *
> + * The function will return -ERESTARTSYS if it was interrupted by a
> + * signal and 0 if @condition evaluated to true.
> + */
> +#define wait_event_interruptible_locked(wq, condition) \
> +({ \
> + int __ret = 0; \
> + if (!(condition)) \
> + __wait_event_interruptible_locked(wq, condition, __ret, 0, , , (&(wq).lock)); \
I had to look more than once to figure out how that code might
return anything else than 0. Can we please change that to
if (!(condition))
__ret = __wait_.....();
to make that less confusing ?
> + __ret; \
> +})
Thanks,
tglx
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