Re: [LTP] [PATCH] mq_open/16-1: use tmp file to share info

[Kang Kai <Kai.Kang@windriver.com>]

On 2012年09月06日 16:08, Jan Stancek wrote:
> On 09/06/2012 07:29 AM, Kang Kai wrote:
>> In this test case, it uses a variable to share data between child and
>> parent processes. But after fork there is a copy of the variable in
>> child process and modify it will not affect the variable in the parent
>> process. Then when the child process call mq_open() before parent
>> process, the case will fail.
>>
>> Use tmp file to replace the variable. Any modification in child process
>> can be seen in parent process.
>>
>> Signed-off-by: Kang Kai<kai.kang@windriver.com>
> This version looks OK to me.

Hi Jan,

>
> I put 2 comments below, but it's nothing serious, in case you would do
> another version you can take it into consideration.
Thanks, I will send a new version. See my comments.

>
> Regards,
> Jan
>
>> ---
>>   .../conformance/interfaces/mq_open/16-1.c          |   39 +++++++++++++++++++-
>>   1 files changed, 37 insertions(+), 2 deletions(-)
>>
>> diff --git a/testcases/open_posix_testsuite/conformance/interfaces/mq_open/16-1.c b/testcases/open_posix_testsuite/conformance/interfaces/mq_open/16-1.c
>> index e07ce86..eadac81 100644
>> --- a/testcases/open_posix_testsuite/conformance/interfaces/mq_open/16-1.c
>> +++ b/testcases/open_posix_testsuite/conformance/interfaces/mq_open/16-1.c
>> @@ -20,9 +20,11 @@
>>    * this is fine (will have some false positives, but no false negatives).
>>    */
>>
>> +#include<sys/mman.h>
>>   #include<sys/stat.h>
>>   #include<sys/types.h>
>>   #include<sys/wait.h>
>> +#include<errno.h>
>>   #include<fcntl.h>
>>   #include<mqueue.h>
>>   #include<signal.h>
>> @@ -32,11 +34,15 @@
>>   #include "posixtest.h"
>>
>>   #define NAMESIZE 50
>> +#define TNAME "mq_open/16-1.c"
>>
>>   int main()
>>   {
>>   	char qname[NAMESIZE];
>> +	char fname[NAMESIZE];
>>   	int pid, succeeded = 0;
>> +	int fd;
>> +	void *pa = NULL;
>>   	mqd_t childqueue, queue;
>>
>>   	/*
>> @@ -47,6 +53,26 @@ int main()
>>
>>   	sprintf(qname, "/mq_open_16-1_%d", getpid());
>>
>> +	sprintf(fname, "/tmp/pts_mq_open_16_1_%d", getpid());
>> +	unlink(fname);
>> +	fd = open(fname, O_CREAT | O_RDWR | O_EXCL,
>> +		 S_IRUSR | S_IWUSR);
>> +	if (fd == -1) {
>> +		printf(TNAME " Error at open(): %s\n", strerror(errno));
>> +		exit(PTS_UNRESOLVED);
>> +	}
>> +	/* file is empty now, will cause "Bus error" */
>> +	write(fd, fname, sizeof(int));
>> +	unlink(fname);
>> +
>> +	pa = mmap(NULL, sizeof(int), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
>> +	if (pa == MAP_FAILED) {
>> +		printf(TNAME " Error at mmap: %s\n", strerror(errno));
>> +		close(fd);
>> +		exit(PTS_FAIL);
>> +	}
>> +	*(int *)pa = 0;
>> +
>>   	pid = fork();
>>   	if (pid == 0) {
>>   		sigset_t mask;
>> @@ -63,7 +89,7 @@ int main()
>>   		childqueue = mq_open(qname, O_CREAT | O_EXCL | O_RDWR,
>>   				     S_IRUSR | S_IWUSR, NULL);
>>   		if (childqueue != (mqd_t) -1) {
>> -			succeeded++;
>> +			++*(int *)pa;
>>   #ifdef DEBUG
>>   			printf("mq_open() in child succeeded\n");
>>   		} else {
> Here we are in child. No close(fd) and munmap()?
I think we should NOT close(fd) and munmap().
In POSIX spec for fork():

* The child process shall have its own copy of the parent’s file 
descriptors. Each of the
child's file descriptors shall refer to the same open file description 
with the corresponding
file descriptor of the parent.
-----------------
If call close(fd), I think the fd is also closed in parent process.

* Memory mappings created in the parent shall be retained in the child 
process.

So munmap() affects both child and parent.


>
>> @@ -80,7 +106,7 @@ int main()
>>   		queue = mq_open(qname, O_CREAT | O_EXCL | O_RDWR,
>>   				S_IRUSR | S_IWUSR, NULL);
>>   		if (queue != (mqd_t) -1) {
>> -			succeeded++;
>> +			++*(int *)pa;
>>   #ifdef DEBUG
>>   			printf("mq_open() in parent succeeded\n");
>>   		} else {
>> @@ -94,6 +120,8 @@ int main()
>>   			mq_close(queue);
>>   			mq_close(childqueue);
>>   			mq_unlink(qname);
>> +			close(fd);
>> +			munmap(pa, sizeof(int));
>>   			return PTS_UNRESOLVED;
>>   		}
>>
>> @@ -101,17 +129,24 @@ int main()
>>   		mq_close(childqueue);
>>   		mq_unlink(qname);
>>
>> +		succeeded = *(int *)pa;
> You could close(fd), munmap() here, then you can remove it from
> all cases below.
OK.

Regards,
Kai

>
>>   		if (succeeded == 0) {
>>   			printf("Test FAILED - mq_open() never succeeded\n");
>> +			close(fd);
>> +			munmap(pa, sizeof(int));
>>   			return PTS_FAIL;
>>   		}
>>
>>   		if (succeeded>  1) {
>>   			printf("Test FAILED - mq_open() succeeded twice\n");
>> +			close(fd);
>> +			munmap(pa, sizeof(int));
>>   			return PTS_FAIL;
>>   		}
>>
>>   		printf("Test PASSED\n");
>> +		close(fd);
>> +		munmap(pa, sizeof(int));
>>   		return PTS_PASS;
>>   	}
>>
>


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