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In pktq_flush(): 

- Run a dummy softint at IPL_SOFTNET on all CPUs to ensure that the
  ISR for this pktqueue is not running (addresses a pre-existing XXX).
- Hold the barrier lock around the critical section to ensure that
  implicit pktq_barrier() calls via pktq_ifdetach() are held off during
  the critical section.
- Ensure the critical section completes in minimal time by not freeing
  memory during the critical section; instead, just build a list of the
  packets pulled out of the per-CPU queues and free them after the critical
  section is over.
This commit is contained in:
thorpej 2022-09-04 17:34:43 +00:00
parent b20f028b5e
commit 06a0da98f2
1 changed files with 31 additions and 6 deletions
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37
sys/net/pktqueue.c
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@ -1,4 +1,4 @@
/* $NetBSD: pktqueue.c,v 1.20 2022/09/02 05:50:36 thorpej Exp $ */
/* $NetBSD: pktqueue.c,v 1.21 2022/09/04 17:34:43 thorpej Exp $ */
/*-
* Copyright (c) 2014 The NetBSD Foundation, Inc.
@ -36,7 +36,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: pktqueue.c,v 1.20 2022/09/02 05:50:36 thorpej Exp $");
__KERNEL_RCSID(0, "$NetBSD: pktqueue.c,v 1.21 2022/09/04 17:34:43 thorpej Exp $");
#ifdef _KERNEL_OPT
#include "opt_net_mpsafe.h"
@ -540,7 +540,23 @@ pktq_flush(pktqueue_t *pq)
{
CPU_INFO_ITERATOR cii;
struct cpu_info *ci;
struct mbuf *m;
struct mbuf *m, *m0 = NULL;
ASSERT_SLEEPABLE();
/*
* Run a dummy softint at IPL_SOFTNET on all CPUs to ensure that any
* already running handler for this pktqueue is no longer running.
*/
xc_barrier(XC_HIGHPRI_IPL(IPL_SOFTNET));
/*
* Acquire the barrier lock. While the caller ensures that
* no explcit pktq_barrier() calls will be issued, this holds
* off any implicit pktq_barrier() calls that would happen
* as the result of pktq_ifdetach().
*/
mutex_enter(&pq->pq_lock);
for (CPU_INFO_FOREACH(cii, ci)) {
struct pcq *q;
@ -550,14 +566,23 @@ pktq_flush(pktqueue_t *pq)
kpreempt_enable();
/*
* XXX This can't be right -- if the softint is running
* then pcq_get isn't safe here.
* Pull the packets off the pcq and chain them into
* a list to be freed later.
*/
while ((m = pcq_get(q)) != NULL) {
pktq_inc_count(pq, PQCNT_DEQUEUE);
m_freem(m);
m->m_nextpkt = m0;
m0 = m;
}
}
mutex_exit(&pq->pq_lock);
/* Free the packets now that the critical section is over. */
while ((m = m0) != NULL) {
m0 = m->m_nextpkt;
m_freem(m);
}
}
static void