[ECOS] pthread_kill and signal lost or pending?

["Zhichao Hong" <zhichao.hong@gmail.com>]

I am having some confusion about how signals are handled in the POSIX
layer.  Basically, I am not sure whether signals can get lost or not
in the eCos implementation.  I created a producer and consumer
threads.  In the producer, I will increment a counter every time when
pthread_kill is called.  And in the consumer which is blocked on
pselect with no signal blocking (zero signal masked), it also
increment a counter whenever it receives a signal.  I found, the
producer called pthread_kill 20 times whereas the consumer only got it
once or twice.  This leads me to think the signals are either pending
forever or lost.  However, when I introduce a mailbox between the
producer and consumer.  Every time when the producer put the message
in the mailbox and then signals the consumer.  On the other side,
consumer get a message and wait for the next signals.  There are still
less signals received than the ones sent (200 sent vs 5 received).
But it seems that the consumer does manage to consume all the messages
the producer sent even with many lost signals.  Can anyone help
explain why this odd behavior occurs?  This is a ARM7TDMI micro.

-- 
Zhichao Hong, CSDP
zhichao.hong@computer.org

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