wangchdo commented on code in PR #17223:
URL: https://github.com/apache/nuttx/pull/17223#discussion_r2455134817
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include/nuttx/event.h:
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@@ -73,7 +73,6 @@ struct nxevent_s
{
struct list_node list; /* Waiting list of nxevent_wait_t */
volatile nxevent_mask_t events; /* Pending Events */
- spinlock_t lock; /* Spinlock */
Review Comment:
This is mainly for removing reliance on semaphore, after removing semaphore,
we will use critical section to protect event, and spinlock is not needed any
more.
The reason to remove semaphore is that it is too heavy for event timeout:
1. It has global big lock inside the sema_wait/sema_post apiļ¼so in fact
there are double lock here: spinlock for event and critical section lock for
semaphore
2. Semaphore object costs more memory
3. It has lost of logic inside sema_wait and sema_post that are not related
to event timeout, these logic is even more complicated than event itself
Indeed the lock scope is very small in event, and after removing semaphore
it is even smaller, so i think this would be better
By the way The current spinlock is also a global one for event post, it uses
`flags = spin_lock_irqsave_nopreempt(&event->lock) `api.
I also submitted #17244 to remove the event's dependency on wait object,
please check detailed information below, thanks
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