On Mon, 2 Jun 2008 14:18:34 +0100
"Eric Kow" <eric.kow@gmail.com> wrote:

> Maybe we can reproduce this more easily by setting PAGER to varying
> values of sleep...

I tried that, with this simple script:

    #!/bin/bash

    i=0
    while true
    do
      i=$[i+3]
      cat >/tmp/mypager <<EOF
    echo Waiting for $i seconds...
    sleep $i
    exit 0
    EOF
      chmod 755 /tmp/mypager
      DARCS_PAGER=/tmp/mypager darcs query a
      echo ok
    done

but for some reason, that does not seem to trigger the problem, at
least not in the first minute or so...

Instead I gave strace enough time: when darcs behave normally, I see
this trace:

    ... 
    wait4(24975, 0x7fff1c389554, 0, NULL)   = ? ERESTARTSYS (To be restarted)
    --- SIGVTALRM (Virtual timer expired) @ 0 (0) ---
    rt_sigreturn(0x1a)                      = 61
    wait4(24975, 0x7fff1c389554, 0, NULL)   = ? ERESTARTSYS (To be restarted)
    --- SIGVTALRM (Virtual timer expired) @ 0 (0) ---
    rt_sigreturn(0x1a)                      = 61
    wait4(24975, 0x7fff1c389554, 0, NULL)   = ? ERESTARTSYS (To be restarted)
    --- SIGVTALRM (Virtual timer expired) @ 0 (0) ---
    write(4, "\377", 1)                     = 1
    rt_sigreturn(0x2)                       = 61
    wait4(24975, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 24975
    --- SIGCHLD (Child exited) @ 0 (0) ---
    unlink("/tmp/darcs-pager24972")         = 0
    getcwd("/home/lele/wip/darcs-2.0", 4096) = 25
    chdir("/home/lele/wip/darcs-2.0")       = 0
    chdir("/home/lele/wip/darcs-2.0")       = 0
    getrusage(RUSAGE_SELF, {ru_utime={0, 192012}, ru_stime={0, 24001}, ...}) = 0
    write(4, "\376", 1)                     = 1
    clock_gettime(0xfffffffe /* CLOCK_??? */, {0, 214695426}) = 0
    rt_sigprocmask(SIG_BLOCK, [HUP INT ABRT PIPE TERM], [], 8) = 0
    rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
    futex(0xbe0eac, 0x85 /* FUTEX_??? */, 1) = 1
    futex(0xbe0ed8, 0x81 /* FUTEX_??? */, 1) = 1
    futex(0xbcad80, 0x81 /* FUTEX_??? */, 1) = 1
    futex(0xbe0eac, 0x85 /* FUTEX_??? */, 1) = 1
    futex(0xbe0ed8, 0x81 /* FUTEX_??? */, 1) = 1
    futex(0xbcad80, 0x81 /* FUTEX_??? */, 1) = 1
    sched_yield()                           = 0
    timer_settime(0, 0, {it_interval={0, 0}, it_value={0, 0}}, NULL) = 0
    timer_delete(0)                         = 0
    fcntl(0, F_GETFL)                       = 0x8002 (flags O_RDWR|O_LARGEFILE)
    fcntl(1, F_GETFL)                       = 0x8002 (flags O_RDWR|O_LARGEFILE)
    fcntl(2, F_GETFL)                       = 0x8002 (flags O_RDWR|O_LARGEFILE)
    rt_sigprocmask(SIG_BLOCK, [TTOU], [], 8) = 0
    rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
    getrusage(RUSAGE_SELF, {ru_utime={0, 192012}, ru_stime={0, 24001}, ...}) = 0
    exit_group(0)                           = ?

But after "threshold" seconds I get this instead:

    ...
    wait4(26621, 0x7fff8c6c6884, 0, NULL)   = ? ERESTARTSYS (To be restarted)
    --- SIGVTALRM (Virtual timer expired) @ 0 (0) ---
    rt_sigreturn(0x1a)                      = 61
    wait4(26621, 0x7fff8c6c6884, 0, NULL)   = ? ERESTARTSYS (To be restarted)
    --- SIGVTALRM (Virtual timer expired) @ 0 (0) ---
    write(4, "\377", 1)                     = 1
    rt_sigreturn(0x2)                       = 61
    wait4(26621, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 26621
    --- SIGCHLD (Child exited) @ 0 (0) ---
    unlink("/tmp/darcs-pager26618")         = 0
    getcwd("/home/lele/wip/darcs-2.0", 4096) = 25
    chdir("/home/lele/wip/darcs-2.0")       = 0
    chdir("/home/lele/wip/darcs-2.0")       = 0
    getrusage(RUSAGE_SELF, {ru_utime={0, 208013}, ru_stime={0, 28001}, ...}) = 0
    write(4, "\376", 1)                     = 1
    clock_gettime(0xfffffffe /* CLOCK_??? */, {0, 231146281}) = 0
    rt_sigprocmask(SIG_BLOCK, [HUP INT ABRT PIPE TERM], [], 8) = 0
    rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
    futex(0xbe10dc, 0x85 /* FUTEX_??? */, 1) = 1
    sched_yield()                           = 0
    sched_yield()                           = 0
    sched_yield()                           = 0
    sched_yield()                           = 0

and that final "sched_yield()" goes on forever... That's the loop that
requires a "kill -9" to be stopped.

ciao, lele.
-- 
nickname: Lele Gaifax    | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas    | comincerò ad aver paura di chi mi copia.
lele@nautilus.homeip.net |                 -- Fortunato Depero, 1929.