On Fri, May 19, 2023 at 08:11:13AM +0200, Claudio Jeker wrote: > On Fri, May 19, 2023 at 01:56:38PM +1000, David Gwynne wrote: > > this is a tiny slice off a big pfsync diff i've been working on. when > > you bring pfsync down i need it to wait until all the work it's been > > doing in the network stack has finished, which means i need a barrier > > for all the network taskqs. that's what this implements. > > > > a barrier per taskq would mean iterating over the taskqs and waiting for > > a barrier on each one. by using a refcnt and shoving a task onto each of > > them in one go, i only have to wait for the slowest one, not all > > of them in series. > > > > ok? > > Not sure if it matters here but wouldn't it be even better to insert this > barrier on the head of the task queue? At least I think you just want one > task run to be done.
that suggestion is a bit triggering for me because: https://cvsweb.openbsd.org/src/sys/kern/kern_task.c#rev1.29 > Now 'ifconfig pfsync0 down' is not a hot path so it does not matter but > such barriers have the tendency to end up in unexpected places. > > Running all tasks in parallel is a good compromise right now. i'd still run the tasks in parallel, even if i queued the barrier work at the head of the taskq. > OK claudio@ > > > Index: if.c > > =================================================================== > > RCS file: /cvs/src/sys/net/if.c,v > > retrieving revision 1.696 > > diff -u -p -r1.696 if.c > > --- if.c 14 May 2023 01:46:53 -0000 1.696 > > +++ if.c 19 May 2023 03:50:10 -0000 > > @@ -3481,3 +3481,19 @@ net_tq(unsigned int ifindex) > > > > return (sn->sn_taskq); > > } > > + > > +void > > +net_tq_barriers(const char *wmesg) > > +{ > > + struct task barriers[NET_TASKQ]; > > + struct refcnt r = REFCNT_INITIALIZER(); > > + int i; > > + > > + for (i = 0; i < nitems(barriers); i++) { > > + task_set(&barriers[i], (void (*)(void *))refcnt_rele_wake, &r); > > + refcnt_take(&r); > > + task_add(softnets[i].sn_taskq, &barriers[i]); > > + } > > + > > + refcnt_finalize(&r, wmesg); > > +} > > Index: if.h > > =================================================================== > > RCS file: /cvs/src/sys/net/if.h,v > > retrieving revision 1.212 > > diff -u -p -r1.212 if.h > > --- if.h 15 May 2023 16:34:56 -0000 1.212 > > +++ if.h 19 May 2023 03:50:10 -0000 > > @@ -560,6 +560,7 @@ int if_congested(void); > > __dead void unhandled_af(int); > > int if_setlladdr(struct ifnet *, const uint8_t *); > > struct taskq * net_tq(unsigned int); > > +void net_tq_barriers(const char *); > > > > #endif /* _KERNEL */ > > > > > > -- > :wq Claudio
