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.
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.
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
