Re: Missed condition-variable wakeups on FreeBSD

On Sun, Feb 27, 2022 at 9:44 AM Andres Freund <andres@anarazel.de> wrote:
> > (gdb) p debug_query_string
> > $1 = 0x21873090 "select count(*) from simple r join simple s using (id);"
> > (gdb) bt
> > #0  _poll () at _poll.S:4
> > #1  0x21701361 in __thr_poll (fds=0x219dc170, nfds=2, timeout=-1) at /usr/src/lib/libthr/thread/thr_syscalls.c:338
> > #2  0x215eaf3f in poll (pfd=0x219dc170, nfds=2, timeout=-1) at /usr/src/lib/libc/sys/poll.c:47
> > #3  0x0097b0fd in WaitEventSetWaitBlock (set=<optimized out>, cur_timeout=-1, occurred_events=<optimized out>,
nevents=<optimizedout>) at latch.c:1171
 
>
> The next time this happens / if you still have this open, perhaps it could be
> worth checking if there's a byte in the self pipe?

As a basic sanity check I'd like to see pfd[0], pfd[1] and the output
of fstat -p PID to see unconsumed bytes in the pipe.  For example
"echo hello | sleep 60" shows "0* pipe ... 6 rw" for sleep, but "echo
hello | more" shows "0* pipe ... 0 rw".