Hello Paul, Eric,
* Paul Eggert wrote on Tue, Jul 20, 2010 at 08:39:45PM CEST:
> System call writes and reads should be atomic, but there's no requirement
> that the shell must implement "echo token" as an atomic write of 6 bytes.
> If the shell sometimes implements "echo token" as multiple writes, that alone
> would explain the problem.
Good point, but wouldn't that be at least a QoI issue for the shell?
> I suggest replacing "echo token" with "echo ''", so that a token
> is always a single newline byte. This may have nothing to do with
> your problem, but it should be done anyway, to make the script
> more portable. And if bash or the kernel does have bugs with respect to
> atomicity, it will make the script less liable to run into the bugs.
OK; that may still be more than one byte on w32 systems, but it's an
improvement nonetheless.
Eric, does this improve tests on your system?
Thanks,
Ralf
2010-07-20 Ralf Wildenhues <ralf.wildenh...@gmx.de>
autotest: use one-byte tokens for more reliable job control.
* lib/autotest/general.m4 (AT_JOB_FIFO_FD): Pass a single
newline.
Suggested by Paul Eggert, bug report by Eric Blake.
diff --git a/lib/autotest/general.m4 b/lib/autotest/general.m4
index e27d601..f4df429 100644
--- a/lib/autotest/general.m4
+++ b/lib/autotest/general.m4
@@ -1386,7 +1386,7 @@ dnl optimize away the _AT_CHECK subshell, so normalize
here.
dnl Ignore PIPE signals that stem from writing back the token.
trap "" PIPE
echo stop > "$at_stop_file"
- echo token >&AT_JOB_FIFO_FD
+ echo >&AT_JOB_FIFO_FD
dnl Do not reraise the default PIPE handler.
dnl It wreaks havoc with ksh, see above.
dnl trap - 13
@@ -1401,7 +1401,7 @@ dnl kill -13 $$
at_failed=:
fi
at_fn_group_postprocess
- echo token >&AT_JOB_FIFO_FD
+ echo >&AT_JOB_FIFO_FD
) &
$at_job_control_off
if $at_first; then
