patacongo commented on code in PR #9528:
URL: https://github.com/apache/nuttx/pull/9528#discussion_r1228411789
##########
sched/group/group_join.c:
##########
@@ -208,9 +218,12 @@ int group_join(FAR struct pthread_tcb_s *tcb)
{
return ret;
}
+#else
+ flags = enter_critical_section();
Review Comment:
There are some special interfaces for this: spin_lock_irqsave() and
spin_unlock_irqrestore(). When SMP is enabled, these use a spinlock to manage
a critical section (and also disable local interrupts).
If SMP is disabled, then it works just like enter_critical_section() (i.e.,
just disables local interrupts).
spin_lock_irqsave is MUCH lighter weight than enter_critical_section() in
SMP mode. That API has to communicate with all of CPUs and assure that they
are all stopped. spin_lock_irqsave() just uses a lightweight spinlock.
sin_lock_irqsave() has more limited usage, however: You can never suspend
the thread if it holds the spinlock whereas you can always wait while holding
the critical section.
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