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condition variables and mutexes
- To: "'eCos Disuss'" <ecos-discuss at sourceware dot cygnus dot com>
- Subject: [ECOS] condition variables and mutexes
- From: "Trenton D. Adams" <tadams at theone dot dnsalias dot com>
- Date: Thu, 9 Aug 2001 15:08:30 -0600
Are the mutexes used with condition variables customarily used for
synchronization with other consumer threads only, or does the producer
thread use the mutexes as well?
I would imagine that the producer thread would generally not use the
mutex associated with a condition variable. I would think that if a
mutex is needed, I should probably create a separate one for my use,
right?
Do I even care about the mutex associated with the condition variable if
I only have one consumer, and one producer?
Here's my situation in particular.
I've created a circular buffer that will hold three times the amount of
data required for each cycle. Cycles usually occur once every second.
I've created three condition/mutex variable pairs for each of the three
slots in the circular buffer.
Producer thread
- fill the first slot of the buffer with the data, and signal the
consumer thread (condition 1)
- fill the second slot of the buffer with the data, and signal the
consumer thread (condition 2)
- fill the third slot of the buffer with the data, and signal the
consumer thread (condition 3)
Consumer thread
loop indefinately
- wait for signal 1
- COPY data to another buffer
- do something with data
- wait for signal 2
- COPY data to another buffer
- do something with data
- wait for signal 3
- COPY data to another buffer
- do something with data
I need a way of making sure that the head pointer of the circular buffer
doesn't change to point to the next slot before the consumer thread has
copied it. I was thinking of using a mutex for this purpose.
Trenton D. Adams
Extreme Engineering
#17, 6025 - 12 St. SE
Calgary, Alberta, Canada
T2H 2K1
Phone: 403 640 9494 ext-208
Fax: 403 640 9599
http://www.extremeeng.com