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Re: callout_stop => callout_halt
Date: 2014年11月17日 01:22:59 +0900
From: Ryota Ozaki <ozaki-r%netbsd.org@localhost>
Here is a patch that includes only ones that require interlock
and rearrangements. Others can be fixed by simply replacing
callout_stop with callout_halt (already committed).
--- a/sys/dev/sysmon/sysmon_envsys_events.c
+++ b/sys/dev/sysmon/sysmon_envsys_events.c
@@ -612,11 +612,19 @@ sme_events_destroy(struct sysmon_envsys *sme)
{
KASSERT(mutex_owned(&sme->sme_mtx));
- callout_stop(&sme->sme_callout);
+ /*
+ * Unset before callout_halt to ensure callout is not scheduled again
+ * during callout_halt
+ */
+ sme->sme_flags &= ~SME_CALLOUT_INITIALIZED;
+
+ mutex_enter(&sme->sme_callout_mtx);
+ callout_halt(&sme->sme_callout, &sme->sme_callout_mtx);
Can't do callout_halt like that because although it unlocks
sme_callout_mtx, it will sleep while sme_mtx is held.
It's not clear why you have to hold sme_callout_mtx here, though -- or
why it even exists independently of sme_mtx. The author of this code
failed to write down any locking rules!
My inclination is to nix sme_callout_mtx altogether and replace every
use of it by sme_mtx (there are obviously some races where one thread
holds one and another thread holds another and they try to touch the
same data structure), but I don't know this code well enough to say
for sure.
+++ b/sys/dev/usb/ohci.c
@@ -350,9 +350,7 @@ ohci_detach(struct ohci_softc *sc, int flags)
if (rv != 0)
return (rv);
- callout_stop(&sc->sc_tmo_rhsc);
-
- usb_delay_ms(&sc->sc_bus, 300); /* XXX let stray task complete */
+ callout_halt(&sc->sc_tmo_rhsc, &sc->sc_intr_lock);
I wouldn't remove the delay just yet -- there may be USB tasks, like I
mentioned earlier, still pending which this completely stupid delay
works around. (If code inspection can rule out the possibility of
such USB tasks, though, go for it.)
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