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

[chrubis@suse.cz]

Hi!
> > > +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.
> 
> Read mentioned here is the one at the beginning of for loop. This line can only
> be reached if that read returned EPIPE. Other failures will end with TBROK.
> If read succeeded this line is never reached, "if (TEST_RETURN != -1)" above
> will break the while loop.

Ah it could be read as imperative sentence too, which confused me
slightly.

I guess that "read has returned EPIPE" would be clearer...

-- 
Cyril Hrubis
chrubis@suse.cz

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