Christopher Faylor <[EMAIL PROTECTED]> wrote:
> If there is no data in a pipe it can wait for 10ms waiting for it, yes.
> See ready_for_read/peek_pipe in select.cc.
Yep i saw the Sleep (10) and though the same thing, but i figured that
can't be it when i commented it out, compiled a new cygwin1.dll and the
10ms delay was still there.
I added some debugging code and narrowed the problem down to five lines.
26 245082 [main] dd 3100 readv: DEBUG 1.a syscalls.cc
23 245105 [main] dd 3100 readv: DEBUG 1.b syscalls.cc
23 245128 [main] dd 3100 readv: DEBUG 2.a syscalls.cc
23 245151 [main] dd 3100 readv: readv (0, 0x240FD9C, 1) blocking, sigcatchers 4
24 245175 [main] dd 3100 readv: DEBUG 2.b syscalls.cc
10508 255683 [main] dd 3100 peek_pipe: DEBUG 7.0 select.cc
76 255759 [main] dd 3100 peek_pipe: /dev/piper, ready for read
27 255786 [main] dd 3100 peek_pipe: DEBUG 7.1 select.cc
25 255811 [main] dd 3100 peek_pipe: DEBUG 7.2 select.cc
26 255837 [main] dd 3100 fhandler_base::ready_for_read: read_ready 1, avail 1
25 255862 [main] dd 3100 readv: DEBUG 2.d syscalls.cc
If i'm not misinterpreting things readv (DEBUG 2.b) is actually the
problem and not peek_pipe. DEBUG 7.0 is always there, even if there is
no delay, so that cannot be it.
Here is the relevant code in syscalls.cc (line 414):
debug_printf ("DEBUG 2.b syscalls.cc");
if (wait && (!cfd->is_slow () || cfd->get_r_no_interrupt ()))
debug_printf ("no need to call ready_for_read");
else if (!cfd->ready_for_read (fd, wait))
{
debug_printf ("DEBUG 2.c syscalls.cc");
res = -1;
goto out;
}
debug_printf ("DEBUG 2.d syscalls.cc");
Now i don't really understand what's going on here. But i hope someone
can explain what the problem is or could be.
Just to save you some work, the code in 1.1.18 where the problem didn't
occur looks like this:
int res;
if (wait && (!sigcatchers || !fh->is_slow () || fh->get_r_no_interrupt ()))
debug_printf ("non-interruptible read\n");
else if (!fh->ready_for_read (fd, wait, 0))
{
if (!wait)
set_sig_errno (EAGAIN); /* Don't really need 'set_sig_errno' here, but... */
else
set_sig_errno (EINTR);
res = -1;
goto out;
}
thomas
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