Semaphores for checking conditions
I'm having some trouble trying to figure out how to use semaphores to control sections that can only be referred to when a variable is in a specific state.
The assumptions are:
- 3 producers produce items to separate buffers A, B and C,
- 2 readers read from the buffers unless empty,
- producer A can only produce if buffer B contains an odd number of elements,
- producer B can only produce if buffer B contains an even or maximum number of elements.
How can I manage the 'if buffer B contains' conditions to avoid the race condition? Can it be done by manipulating the value of the semaphore directly or should it be done in another way?
I have so far implemented shared memory for buffers, semaphores FULL and EMPTY for each buffer and a semaphore that blocks access to the sections refering to the shared memory when in use and I can't think of a solution that would work for that.
c semaphore shared-memory race-condition
asked Dec 27 '18 at 23:55
A.Z.
11
add a comment |
I'm having some trouble trying to figure out how to use semaphores to control sections that can only be referred to when a variable is in a specific state.
The assumptions are:
- 3 producers produce items to separate buffers A, B and C,
- 2 readers read from the buffers unless empty,
- producer A can only produce if buffer B contains an odd number of elements,
- producer B can only produce if buffer B contains an even or maximum number of elements.
How can I manage the 'if buffer B contains' conditions to avoid the race condition? Can it be done by manipulating the value of the semaphore directly or should it be done in another way?
I have so far implemented shared memory for buffers, semaphores FULL and EMPTY for each buffer and a semaphore that blocks access to the sections refering to the shared memory when in use and I can't think of a solution that would work for that.
c semaphore shared-memory race-condition
asked Dec 27 '18 at 23:55
A.Z.
11
Is the code multi-threaded or multi-process?
– user3386109
Dec 28 '18 at 0:22
For a basic understanding, you can check out en.wikipedia.org/wiki/Dining_philosophers_problem and en.wikipedia.org/wiki/Producer%E2%80%93consumer_problem
– visibleman
Dec 28 '18 at 0:27
It's multi-process.
– A.Z.
Dec 28 '18 at 12:38
add a comment |
I'm having some trouble trying to figure out how to use semaphores to control sections that can only be referred to when a variable is in a specific state.
The assumptions are:
- 3 producers produce items to separate buffers A, B and C,
- 2 readers read from the buffers unless empty,
- producer A can only produce if buffer B contains an odd number of elements,
- producer B can only produce if buffer B contains an even or maximum number of elements.
How can I manage the 'if buffer B contains' conditions to avoid the race condition? Can it be done by manipulating the value of the semaphore directly or should it be done in another way?
I have so far implemented shared memory for buffers, semaphores FULL and EMPTY for each buffer and a semaphore that blocks access to the sections refering to the shared memory when in use and I can't think of a solution that would work for that.
c semaphore shared-memory race-condition
asked Dec 27 '18 at 23:55
A.Z.
11
I'm having some trouble trying to figure out how to use semaphores to control sections that can only be referred to when a variable is in a specific state.
The assumptions are:
- 3 producers produce items to separate buffers A, B and C,
- 2 readers read from the buffers unless empty,
- producer A can only produce if buffer B contains an odd number of elements,
- producer B can only produce if buffer B contains an even or maximum number of elements.
How can I manage the 'if buffer B contains' conditions to avoid the race condition? Can it be done by manipulating the value of the semaphore directly or should it be done in another way?
I have so far implemented shared memory for buffers, semaphores FULL and EMPTY for each buffer and a semaphore that blocks access to the sections refering to the shared memory when in use and I can't think of a solution that would work for that.
c semaphore shared-memory race-condition
c semaphore shared-memory race-condition
asked Dec 27 '18 at 23:55
A.Z.
11
asked Dec 27 '18 at 23:55
A.Z.
11
asked Dec 27 '18 at 23:55
A.Z.
11
asked Dec 27 '18 at 23:55
A.Z.
11
asked Dec 27 '18 at 23:55
A.Z.
11
11
Is the code multi-threaded or multi-process?
– user3386109
Dec 28 '18 at 0:22
For a basic understanding, you can check out en.wikipedia.org/wiki/Dining_philosophers_problem and en.wikipedia.org/wiki/Producer%E2%80%93consumer_problem
– visibleman
Dec 28 '18 at 0:27
It's multi-process.
– A.Z.
Dec 28 '18 at 12:38
add a comment |
Is the code multi-threaded or multi-process?
– user3386109
Dec 28 '18 at 0:22
For a basic understanding, you can check out en.wikipedia.org/wiki/Dining_philosophers_problem and en.wikipedia.org/wiki/Producer%E2%80%93consumer_problem
– visibleman
Dec 28 '18 at 0:27
It's multi-process.
– A.Z.
Dec 28 '18 at 12:38
Is the code multi-threaded or multi-process?
– user3386109
Dec 28 '18 at 0:22
Is the code multi-threaded or multi-process?
– user3386109
Dec 28 '18 at 0:22
For a basic understanding, you can check out en.wikipedia.org/wiki/Dining_philosophers_problem and en.wikipedia.org/wiki/Producer%E2%80%93consumer_problem
– visibleman
Dec 28 '18 at 0:27
For a basic understanding, you can check out en.wikipedia.org/wiki/Dining_philosophers_problem and en.wikipedia.org/wiki/Producer%E2%80%93consumer_problem
– visibleman
Dec 28 '18 at 0:27
It's multi-process.
– A.Z.
Dec 28 '18 at 12:38
It's multi-process.
– A.Z.
Dec 28 '18 at 12:38
add a comment |
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Is the code multi-threaded or multi-process?
– user3386109
Dec 28 '18 at 0:22
For a basic understanding, you can check out en.wikipedia.org/wiki/Dining_philosophers_problem and en.wikipedia.org/wiki/Producer%E2%80%93consumer_problem
– visibleman
Dec 28 '18 at 0:27
It's multi-process.
– A.Z.
Dec 28 '18 at 12:38