[haiku-bugs] [Haiku] #11208: POSIX semaphores have incorrect sharing semantics
- From: "hamish" <trac@xxxxxxxxxxxx>
- Date: Sat, 06 Sep 2014 20:40:26 -0000
#11208: POSIX semaphores have incorrect sharing semantics
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Reporter: hamish | Owner: nobody
Type: bug | Status: new
Priority: normal | Milestone: R1
Component: System/POSIX | Version: R1/Development
Keywords: | Blocked By:
Blocking: | Has a Patch: 0
Platform: All |
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POSIX semaphores should only be shared between processes if a non-zero
pshared value is given to `sem_init`, and the semaphore resides in a
shared region of memory (like a `PTHREAD_PROCESS_SHARED` mutex). The POSIX
spec is not explicit about it, but this is how Linux and FreeBSD behave.
Haiku ignores the latter requirement, so pshared semaphores in private
memory (e.g. the stack or heap) are shared after a fork.
Test case:
{{{
#include <semaphore.h>
#include <unistd.h>
#include <assert.h>
#include <stdio.h>
int main() {
sem_t sem;
int res = sem_init(&sem, 1, 0);
assert(res == 0);
int pid = fork();
assert(pid != -1);
if (pid == 0) {
res = sem_post(&sem);
assert(res == 0);
} else {
res = sem_wait(&sem);
assert(res == 0);
}
printf("End\n");
return 0;
}
}}}
The parent process should wait indefinitely on the semaphore, but it does
not.
--
Ticket URL: <https://dev.haiku-os.org/ticket/11208>
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