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Implement softint_schedule_cpu() for rump kernels.

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While distributing processing all over the place is not relevant for
high-performance rump kernel I/O stacks (and downright counterproductive),
the mechanism is used e.g. to reach a quiescent state when detaching
an interface, and therefore a semantically correct implementation is
required.

Fixes at least an uncommon race in the ifconfig destroy case.
reported & patch tested by Justin Cormack.
This commit is contained in:
pooka 2015-01-14 18:46:38 +00:00
parent b4b3a81a2a
commit e82a50e44e
1 changed files with 104 additions and 8 deletions
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112
sys/rump/librump/rumpkern/intr.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: intr.c,v 1.46 2014/06/22 20:09:19 pooka Exp $ */
/* $NetBSD: intr.c,v 1.47 2015/01/14 18:46:38 pooka Exp $ */
/*
* Copyright (c) 2008-2010 Antti Kantee. All Rights Reserved.
@ -26,7 +26,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: intr.c,v 1.46 2014/06/22 20:09:19 pooka Exp $");
__KERNEL_RCSID(0, "$NetBSD: intr.c,v 1.47 2015/01/14 18:46:38 pooka Exp $");
#include <sys/param.h>
#include <sys/atomic.h>
@ -62,8 +62,10 @@ struct softint {
struct softint_percpu {
struct softint *sip_parent;
bool sip_onlist;
bool sip_onlist_cpu;
LIST_ENTRY(softint_percpu) sip_entries;
LIST_ENTRY(softint_percpu) sip_entries; /* scheduled */
TAILQ_ENTRY(softint_percpu) sip_entries_cpu; /* to be scheduled */
};
struct softint_lev {
@ -71,6 +73,11 @@ struct softint_lev {
LIST_HEAD(, softint_percpu) si_pending;
};
static TAILQ_HEAD(, softint_percpu) sicpupending \
= TAILQ_HEAD_INITIALIZER(sicpupending);
static struct rumpuser_mtx *sicpumtx;
static struct rumpuser_cv *sicpucv;
kcondvar_t lbolt; /* Oh Kath Ra */
static u_int ticks;
@ -183,6 +190,51 @@ sithread(void *arg)
panic("sithread unreachable");
}
/*
* Helper for softint_schedule_cpu()
*/
static void
sithread_cpu_bouncer(void *arg)
{
struct lwp *me;
me = curlwp;
me->l_pflag |= LP_BOUND;
rump_unschedule();
for (;;) {
struct softint_percpu *sip;
struct softint *si;
struct cpu_info *ci;
unsigned int cidx;
rumpuser_mutex_enter_nowrap(sicpumtx);
while (TAILQ_EMPTY(&sicpupending)) {
rumpuser_cv_wait_nowrap(sicpucv, sicpumtx);
}
sip = TAILQ_FIRST(&sicpupending);
TAILQ_REMOVE(&sicpupending, sip, sip_entries_cpu);
sip->sip_onlist_cpu = false;
rumpuser_mutex_exit(sicpumtx);
/*
* ok, now figure out which cpu we need the softint to
* be handled on
*/
si = sip->sip_parent;
cidx = sip - si->si_entry;
ci = cpu_lookup(cidx);
me->l_target_cpu = ci;
/* schedule ourselves there, and then schedule the softint */
rump_schedule();
KASSERT(curcpu() == ci);
softint_schedule(si);
rump_unschedule();
}
panic("sithread_cpu_bouncer unreasonable");
}
static kmutex_t sithr_emtx;
static unsigned int sithr_est;
static int sithr_canest;
@ -273,6 +325,13 @@ softint_init(struct cpu_info *ci)
if ((rv = kthread_create(PRI_NONE, KTHREAD_MPSAFE,
ci, doclock, NULL, NULL, "rumpclk%d", ci->ci_index)) != 0)
panic("clock thread creation failed: %d", rv);
/* not one either, but at least a softint helper */
rumpuser_mutex_init(&sicpumtx, RUMPUSER_MTX_SPIN);
rumpuser_cv_init(&sicpucv);
if ((rv = kthread_create(PRI_NONE, KTHREAD_MPSAFE,
NULL, sithread_cpu_bouncer, NULL, NULL, "sipbnc")) != 0)
panic("softint cpu bouncer creation failed: %d", rv);
}
void *
@ -300,6 +359,13 @@ softint_establish(u_int flags, void (*func)(void *), void *arg)
return si;
}
static struct softint_percpu *
sitosip(struct softint *si, struct cpu_info *ci)
{
return &si->si_entry[ci->ci_index];
}
/*
* Soft interrupts bring two choices. If we are running with thread
* support enabled, defer execution, otherwise execute in place.
@ -310,7 +376,7 @@ softint_schedule(void *arg)
{
struct softint *si = arg;
struct cpu_info *ci = curcpu();
struct softint_percpu *sip = &si->si_entry[ci->ci_index];
struct softint_percpu *sip = sitosip(si, ci);
struct cpu_data *cd = &ci->ci_data;
struct softint_lev *si_lvl = cd->cpu_softcpu;
@ -325,14 +391,44 @@ softint_schedule(void *arg)
}
}
/*
* Like softint_schedule(), except schedule softint to be handled on
* the core designated by ci_tgt instead of the core the call is made on.
*
* Unlike softint_schedule(), the performance is not important
* (unless ci_tgt == curcpu): high-performance rump kernel I/O stacks
* should arrange data to already be on the right core at the driver
* layer.
*/
void
softint_schedule_cpu(void *arg, struct cpu_info *ci)
softint_schedule_cpu(void *arg, struct cpu_info *ci_tgt)
{
struct softint *si = arg;
struct cpu_info *ci_cur = curcpu();
struct softint_percpu *sip;
KASSERT(rump_threads);
/* preferred case (which can be optimized some day) */
if (ci_cur == ci_tgt) {
softint_schedule(si);
return;
}
/*
* TODO: implement this properly
* no? then it's softint turtles all the way down
*/
KASSERT(curcpu() == ci);
softint_schedule(arg);
sip = sitosip(si, ci_tgt);
rumpuser_mutex_enter_nowrap(sicpumtx);
if (sip->sip_onlist_cpu) {
rumpuser_mutex_exit(sicpumtx);
return;
}
TAILQ_INSERT_TAIL(&sicpupending, sip, sip_entries_cpu);
sip->sip_onlist_cpu = true;
rumpuser_cv_signal(sicpucv);
rumpuser_mutex_exit(sicpumtx);
}
/*