Clive Wilson wrote:
At 10:20 31/05/2007, you wrote:
So waiting on a semaphore would mean:
lock mutex
while (count==0)
wait on condition variable
count--
unlock mutex
And posting a semaphore:
lock mutex
count++
signal condition variable
unlock mutex
Jonathan,
As a clarification of the above example, is the intention for the mutex
used by the semaphore pend to be the same as the one used by the
semaphore post? I imagine not, otherwise the pend would wait on the
condition variable with the mutex locked, therefore preventing a post
from occurring...
It is the same mutex. Condition variables always have a mutex associated
with them. When you wait on a CV, the mutex is automatically unlocked by
the OS, and when you wake up after the CV is signalled, the OS
automatically relocks the mutex before the wait function returns.
Jifl
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