On 11/13/2013 12:46 PM, Jan Stancek wrote:
>
> ----- Original Message -----
>> From: "Stanislav Kholmanskikh" <stanislav.kholmansk...@oracle.com>
>> To: ltp-list@lists.sourceforge.net
>> Cc: "vasily isaenko" <vasily.isae...@oracle.com>
>> Sent: Wednesday, 13 November, 2013 8:52:42 AM
>> Subject: [LTP] [RFC PATCH] tst_checkpoint_signal_child: implemented timeout
>>
>> If a child exits before opening TST_CHECKPOINT_FIFO
>> for reading, tst_checkpoint_signal_child() issued from the parent
>> will block forever.
>>
>> To handle such situations added timeout logic to
>> tst_checkpoint_signal_child();
>>
>> Signed-off-by: Stanislav Kholmanskikh <stanislav.kholmansk...@oracle.com>
>> ---
>> lib/tst_checkpoint.c | 56
>> ++++++++++++++++++++++++++++++++++++++++++++++++-
>> 1 files changed, 54 insertions(+), 2 deletions(-)
> Hi,
>
> I would go with just 2 return values:
> -1 - for error/timeout
> fd - otherwise
>
> fd == 0 is a valid descriptor
> we can tell if it was timeout or error by errno code
Hi.
Ok.
> Why do we need "saved_errno"?
Initially I though to use "saved_errno" to handle this situation:
* nanosleep() fails and updates global errno
* open_wronly_timed() returns
But I've looked again on the code and It seems that this situation will
not happen and so on "saved_errno" is useless...
Thanks.
>
> Regards,
> Jan
>
>> diff --git a/lib/tst_checkpoint.c b/lib/tst_checkpoint.c
>> index 56c86b5..a7936da 100644
>> --- a/lib/tst_checkpoint.c
>> +++ b/lib/tst_checkpoint.c
>> @@ -30,9 +30,54 @@
>> #include <sys/stat.h>
>> #include <fcntl.h>
>> #include <poll.h>
>> +#include <time.h>
>>
>> #include "tst_checkpoint.h"
>>
>> +/*
>> + * Issue open() on 'path' fifo with O_WRONLY flag and wait for
>> + * a reader up to 'timeout' ms.
>> + *
>> + * Returns:
>> + * 0 - timeout has happened
>> + * > 0 - file descriptor
>> + * -1 - an error has occurred (errno is set accordingly)
>> + *
>> + */
>> +int open_wronly_timed(const char *path, unsigned int timeout)
>> +{
>> + int fd;
>> + int interval_ms = 1; /* how often issue open(O_NONBLOCK) */
>> + long timeleft = timeout;
>> + int saved_errno = errno;
>> +
>> + struct timespec interval;
>> + interval.tv_sec = 0;
>> + interval.tv_nsec = interval_ms * 1000000; /* in ns */
>> +
>> + for (;;) {
>> + fd = open(path, O_WRONLY | O_NONBLOCK);
>> + if (fd < 0) {
>> + if ((errno == ENXIO) || (errno == EINTR)) {
>> + if (timeleft <= 0) {
>> + errno = saved_errno;
>> +
>> + return 0;
>> + }
>> +
>> + timeleft -= interval_ms;
>> + nanosleep(&interval, NULL);
>> +
>> + continue;
>> + }
>> +
>> + return -1;
>> + }
>> +
>> + return fd;
>> + }
>> +}
>> +
>> void tst_checkpoint_init(const char *file, const int lineno,
>> struct tst_checkpoint *self)
>> {
>> @@ -195,12 +240,19 @@ void tst_checkpoint_signal_child(const char *file,
>> const int lineno,
>> {
>> int ret, fd;
>>
>> - fd = open(TST_CHECKPOINT_FIFO, O_WRONLY);
>> + fd = open_wronly_timed(TST_CHECKPOINT_FIFO, self->timeout);
>>
>> - if (fd < 0) {
>> + switch (fd) {
>> + case 0:
>> + tst_brkm(TBROK, cleanup_fn,
>> + "Checkpoint timeouted after %u msecs at %s:%d",
>> + self->timeout, file, lineno);
>> + break;
>> + case -1:
>> tst_brkm(TBROK | TERRNO, cleanup_fn,
>> "Failed to open fifo '%s' at %s:%d",
>> TST_CHECKPOINT_FIFO, file, lineno);
>> + break;
>> }
>>
>> ret = write(fd, "p", 1);
>> --
>> 1.7.1
>>
>>
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