Hi Scott,
I looked at your patch and it seemed to work fine. I submitted it to trunk.
Thank you,
Niels.
On 2/24/07, Scott Lamb <[EMAIL PROTECTED]> wrote:
On Feb 22, 2007, at 6:32 PM, Niels Provos wrote:
> Do you have an addition to the regression test that would allow me to
> verify that the new code works as intended? If not, it would be most
> appreciated :-)
Happy Weekend, everyone. Looking at this again.
There are two regression tests for this now:
* test_simplesignal() tests a signal delivered while within select()/
poll()/kevent()/epoll()/whatever.
* test_immediatesignal() tests a signal delivered between signal_add
() and event_loop().
But you're referring to something more...proving that there would
have been an evsignal_process() race if not for the reordering,
right? That's hard to do through regression tests. I can think of
only a couple ways to do that:
(1) loop trying it many times, scheduling later delivery with alarms
or through an additional thread (tests would depend on pthreads).
Probably have to add some instrumentation to evsignal_process() to
make it sleep at particular times to make it likely enough to happen
on demand.
(2) use debugging mechanisms to step through and deliver the signal
at a particular time. I actually have done this programmatically
before when proving a signal-handling library [*], but it was a lot
of code and not exactly the most portable. Maybe it could be done
more easily with gdb and expect, on at least gdb platforms.
Would it help if I showed you a way to test it by hand?
I've attached a simple test program that registers a handler for
SIGUSR1 and SIGUSR2 which simply notes the signal was received. You
can see the races I mention with gdb as follows:
$ gcc -Wall sigtest.c -o sigtest -L.libs -levent
$ LD_LIBRARY_PATH=.libs gdb ./sigtest
...
(gdb) break evsignal_process
Function "evsignal_process" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (evsignal_process) pending.
(gdb) run
Starting program: /home/slamb/svn/libevent/sigtest
(no debugging symbols found)
<<<hit ctrl-C>>>
Breakpoint 2 at 0x2aaaaaabf4a0: file signal.c, line 165.
Pending breakpoint "evsignal_process" resolved
Program received signal SIGINT, Interrupt.
0x000000318a4cd9d3 in __epoll_wait_nocancel () from /lib64/libc.so.6
(gdb) signal SIGUSR1
Breakpoint 2, evsignal_process () at signal.c:165 (my line numbers
are off because I've #ifdefed the two code blocks)
<<<step until you hit a place you're suspicious of>>>
(gdb) n
179 memset(evsigcaught, 0, sizeof(evsigcaught));
(gdb) signal SIGUSR2
Continuing with signal SIGUSR2.
Received signal 10
Here you can see that it only acknowledged receipt of SIGUSR1;
SIGUSR2 was lost.
If you do the same thing at any point in my modified evsignal_process
(), you find instead:
(gdb) signal SIGUSR2
Continuing with signal SIGUSR2.
Received signal 10
Breakpoint 2, evsignal_process () at signal.c:165
165 {
(gdb) c
Continuing.
Received signal 12
[*] http://www.slamb.org/svn/repos/trunk/projects/sigsafe/tests/
race_checker/
--
Scott Lamb <http://www.slamb.org/>
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