[tor-bugs] #23538 [Core Tor/Tor]: Allow KISTSchedRunInterval to be negative

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#23538: Allow KISTSchedRunInterval to be negative
-----------------------------+------------------------------------
 Reporter:  pastly           |          Owner:  (none)
     Type:  defect           |         Status:  new
 Priority:  Medium           |      Milestone:  Tor: 0.3.2.x-final
Component:  Core Tor/Tor     |        Version:
 Severity:  Normal           |     Resolution:
 Keywords:  tor-sched, easy  |  Actual Points:
Parent ID:                   |         Points:
 Reviewer:                   |        Sponsor:
-----------------------------+------------------------------------

Comment (by pastly):

 {{{
 diff --git a/src/or/config.c b/src/or/config.c
 index 4ee140381..70203a801 100644
 --- a/src/or/config.c
 +++ b/src/or/config.c
 @@ -491,7 +491,7 @@ static config_var_t option_vars_[] = {
    OBSOLETE("SchedulerLowWaterMark__"),
    OBSOLETE("SchedulerHighWaterMark__"),
    OBSOLETE("SchedulerMaxFlushCells__"),
 -  V(KISTSchedRunInterval,        MSEC_INTERVAL, "0 msec"),
 +  V(KISTSchedRunInterval,        INT, "0 msec"),
    V(KISTSockBufSizeFactor,       DOUBLE,   "1.0"),
    V(Schedulers,                  CSV,      "KIST,KISTLite,Vanilla"),
    V(ShutdownWaitLength,          INTERVAL, "30 seconds"),
 @@ -2974,7 +2974,7 @@ options_validate_scheduler(or_options_t *options,
 char **msg)

    /* Don't need to validate that the Interval is less than anything
 because
     * zero is valid and all negative values are valid. */
 -  if (options->KISTSchedRunInterval > KIST_SCHED_RUN_INTERVAL_MAX) {
 +  if ((int)options->KISTSchedRunInterval > KIST_SCHED_RUN_INTERVAL_MAX) {
      tor_asprintf(msg, "KISTSchedRunInterval must not be more than %d
 (ms)",
                   KIST_SCHED_RUN_INTERVAL_MAX);
      return -1;
 }}}

 This is all that is needed if to allow negative values. HOWEVER. Actually
 using one leads to

 {{{
 Sep 18 11:06:22.897 [notice] Scheduler type KIST has been disabled by the
 consensus.
 Sep 18 11:06:22.897 [notice] Scheduler type KISTLite has been enabled.
 Sep 18 11:06:22.897 [warn] tor_bug_occurred_(): Bug:
 src/or/scheduler_kist.c:495: kist_scheduler_init: Non-fatal assertion
 !((sched_run_interval <= 0)) failed. (Future instances of this warning
 will be silenced.) (on Tor 0.3.2.0-alpha-dev c7af923567bca5b0)
 Sep 18 11:06:22.897 [warn] Bug: Non-fatal assertion !((sched_run_interval
 <= 0)) failed in kist_scheduler_init at src/or/scheduler_kist.c:495. Stack
 trace: (on Tor 0.3.2.0-alpha-dev c7af923567bca5b0)
 Sep 18 11:06:22.897 [warn] Bug:     ./src/or/tor(log_backtrace+0x42)
 [0x55b43214dcc2] (on Tor 0.3.2.0-alpha-dev c7af923567bca5b0)
 Sep 18 11:06:22.897 [warn] Bug:     ./src/or/tor(tor_bug_occurred_+0xb9)
 [0x55b432168df9] (on Tor 0.3.2.0-alpha-dev c7af923567bca5b0)
 Sep 18 11:06:22.897 [warn] Bug:     ./src/or/tor(+0xb8a0f)
 [0x55b432084a0f] (on Tor 0.3.2.0-alpha-dev c7af923567bca5b0)
 Sep 18 11:06:22.897 [warn] Bug:     ./src/or/tor(set_options+0x17d6)
 [0x55b4320c6166] (on Tor 0.3.2.0-alpha-dev c7af923567bca5b0)
 Sep 18 11:06:22.897 [warn] Bug:
 ./src/or/tor(options_init_from_string+0x34a) [0x55b4320c71ca] (on Tor
 0.3.2.0-alpha-dev c7af923567bca5b0)
 Sep 18 11:06:22.897 [warn] Bug:
 ./src/or/tor(options_init_from_torrc+0x1be) [0x55b4320c754e] (on Tor
 0.3.2.0-alpha-dev c7af923567bca5b0)
 Sep 18 11:06:22.897 [warn] Bug:     ./src/or/tor(tor_init+0x303)
 [0x55b43201e283] (on Tor 0.3.2.0-alpha-dev c7af923567bca5b0)
 Sep 18 11:06:22.897 [warn] Bug:     ./src/or/tor(tor_main+0x5f)
 [0x55b43201f6bf] (on Tor 0.3.2.0-alpha-dev c7af923567bca5b0)
 Sep 18 11:06:22.897 [warn] Bug:     ./src/or/tor(main+0x19)
 [0x55b432019179] (on Tor 0.3.2.0-alpha-dev c7af923567bca5b0)
 Sep 18 11:06:22.897 [warn] Bug:
 /lib64/libc.so.6(__libc_start_main+0xf0) [0x7f3952fd4640] (on Tor 0.3.2.0
 -alpha-dev c7af923567bca5b0)
 Sep 18 11:06:22.897 [warn] Bug:     ./src/or/tor(_start+0x29)
 [0x55b4320191c9] (on Tor 0.3.2.0-alpha-dev c7af923567bca5b0)
 Sep 18 11:06:22.897 [warn] We are initing the KIST scheduler and noticed
 the KISTSchedRunInterval is telling us to not use KIST. That's weird!
 We'll continue using KIST, but at 10ms.
 }}}

 1. It wasn't disabled by the consensus. It was disabled by the user.
 2. It would be nice if we removed kist schedulers from the Schedulers
 torrc option when the interval asks for kist to be disabled
 3. We need to not use kist

 Maybe ... just maybe ... using a negative run interval is obsolete logic
 and the Schedulers option should be the way to disable KIST :) That might
 be simpler.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23538#comment:2>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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