Re: [LTP] [PATCH v2] new testcase: kmsg01

[chrubis@suse.cz]

Hi!
> +static int timed_read_kmsg(int fd, int timeout_sec)
> +{
> +	int child, status, ret = 0;
> +	int pipefd[2];
> +	char msg[MAX_MSGSIZE];
> +
> +	if (pipe(pipefd) != 0)
> +		tst_brkm(TBROK|TERRNO, cleanup, "pipe failed");
> +
> +	child = fork();
> +	switch (child) {
> +	case -1:
> +		tst_brkm(TBROK|TERRNO, cleanup, "failed to fork");
> +	case 0:
> +		/* child does all the reading and keeps writing to
> +		 * pipe to let parent know that it didn't block */
> +		SAFE_CLOSE(NULL, pipefd[0]);

There is a problem with calling the SAFE_ macros from child processes.
The SAFE_ macros use tst_brkm() interface to halt program execution (in
case of failure) which is not supposed to be used from child and may
lead to unexpected results.

> +static void test_seek(void)
> +{
> +	int k, j = NUM_READ_RETRY, fd;
> +	char msg[MAX_MSGSIZE];
> +	unsigned long seqno[2];
> +
> +	/* 1. read() after SEEK_SET 0 returns same (first) message */
> +	tst_resm(TINFO, "TEST: seek SEEK_SET 0");
> +
> +	fd = open("/dev/kmsg", O_RDONLY | O_NONBLOCK);
> +	if (fd < 0)
> +		tst_brkm(TBROK|TERRNO, cleanup,	"failed to open /dev/kmsg");
> +
> +	while (j) {
> +		for (k = 0; k < 2; k++) {
> +			TEST(read(fd, msg, sizeof(msg)));
> +			if (TEST_RETURN == -1) {
> +				if (errno == EPIPE)
> +					break;
> +				else
> +					tst_brkm(TBROK|TTERRNO, cleanup,
> +						"failed to read /dev/kmsg");
> +			}
> +			if (get_msg_fields(msg, NULL, &seqno[k]) != 0)
> +				tst_resm(TFAIL, "failed to parse seqid: %s",
> +					msg);
> +			if (k == 0)
> +				if (lseek(fd, 0, SEEK_SET) == -1)
> +					tst_resm(TFAIL|TERRNO,
> +						"SEEK_SET 0 failed");
> +		}
> +
> +		if (TEST_RETURN != -1)
> +			break;
> +
> +		/* give a second to whoever overwrote first message to finish */
> +		sleep(1);
> +		j--;
> +
> +		/* read returned EPIPE, reopen fd and try again */
> +		SAFE_CLOSE(cleanup, fd);
> +		fd = open("/dev/kmsg", O_RDONLY | O_NONBLOCK);
> +		if (fd < 0)
> +			tst_brkm(TBROK|TERRNO, cleanup,
> +				"failed to open /dev/kmsg");

I guess that the comment says something different than the code, there
is no read involved here.


Acked with change from SAFE_CLOSE() to close() in the child process.

-- 
Cyril Hrubis
chrubis@suse.cz

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