POSIX doesn't state that if mmap() is given only PROT_WRITE, then
that memory region will have read access too. It's an implementation
issue of the platform.
On a platform which don't imply read access when only PROT_WRITE is given,
such a situation happens:
1) a child process decrements the semaphore with sem_wait(sem)
2) then tries to dereference create_cnt via (*create_cnt)++. This
will result in a SIGSEGV, and the child will be terminated.
Therefore the semaphore will be left in a "decremented" state and this
test case will hang.
To overcome this problem we should explicitly pass PROT_READ to mmap().
Signed-off-by: Stanislav Kholmanskikh <[email protected]>
---
.../conformance/interfaces/shm_open/23-1.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git
a/testcases/open_posix_testsuite/conformance/interfaces/shm_open/23-1.c
b/testcases/open_posix_testsuite/conformance/interfaces/shm_open/23-1.c
index 40d7a19..7a82f88 100644
--- a/testcases/open_posix_testsuite/conformance/interfaces/shm_open/23-1.c
+++ b/testcases/open_posix_testsuite/conformance/interfaces/shm_open/23-1.c
@@ -105,7 +105,7 @@ int main(void)
return PTS_UNRESOLVED;
}
- create_cnt = mmap(NULL, sizeof(*create_cnt), PROT_WRITE,
+ create_cnt = mmap(NULL, sizeof(*create_cnt), PROT_WRITE | PROT_READ,
MAP_SHARED, result_fd, 0);
if (create_cnt == MAP_FAILED) {
perror("An error occurs when calling mmap()");
--
1.7.1
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