From 5719b296fb81502d0dbbb4e87b3235e5bdcdfc6b Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Thu, 23 Jul 2015 12:05:39 +0200 Subject: [PATCH] inet: frag: don't wait for timer deletion when evicting Frank reports 'NMI watchdog: BUG: soft lockup' errors when load is high. Instead of (potentially) unbounded restarts of the eviction process, just skip to the next entry. One caveat is that, when a netns is exiting, a timer may still be running by the time inet_evict_bucket returns. We use the frag memory accounting to wait for outstanding timers, so that when we free the percpu counter we can be sure no running timer will trip over it. Reported-and-tested-by: Frank Schreuder Signed-off-by: Florian Westphal Signed-off-by: David S. Miller --- net/ipv4/inet_fragment.c | 29 +++++++++++------------------ 1 file changed, 11 insertions(+), 18 deletions(-) diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c index 4473232e4e88..a00ca4c00c35 100644 --- a/net/ipv4/inet_fragment.c +++ b/net/ipv4/inet_fragment.c @@ -131,24 +131,14 @@ inet_evict_bucket(struct inet_frags *f, struct inet_frag_bucket *hb) unsigned int evicted = 0; HLIST_HEAD(expired); -evict_again: spin_lock(&hb->chain_lock); hlist_for_each_entry_safe(fq, n, &hb->chain, list) { if (!inet_fragq_should_evict(fq)) continue; - if (!del_timer(&fq->timer)) { - /* q expiring right now thus increment its refcount so - * it won't be freed under us and wait until the timer - * has finished executing then destroy it - */ - atomic_inc(&fq->refcnt); - spin_unlock(&hb->chain_lock); - del_timer_sync(&fq->timer); - inet_frag_put(fq, f); - goto evict_again; - } + if (!del_timer(&fq->timer)) + continue; fq->flags |= INET_FRAG_EVICTED; hlist_add_head(&fq->list_evictor, &expired); @@ -239,18 +229,20 @@ void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f) int i; nf->low_thresh = 0; - local_bh_disable(); evict_again: + local_bh_disable(); seq = read_seqbegin(&f->rnd_seqlock); for (i = 0; i < INETFRAGS_HASHSZ ; i++) inet_evict_bucket(f, &f->hash[i]); - if (read_seqretry(&f->rnd_seqlock, seq)) - goto evict_again; - local_bh_enable(); + cond_resched(); + + if (read_seqretry(&f->rnd_seqlock, seq) || + percpu_counter_sum(&nf->mem)) + goto evict_again; percpu_counter_destroy(&nf->mem); } @@ -284,6 +276,7 @@ static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f) hb = get_frag_bucket_locked(fq, f); hlist_del(&fq->list); + fq->flags |= INET_FRAG_COMPLETE; spin_unlock(&hb->chain_lock); } @@ -295,7 +288,6 @@ void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f) if (!(fq->flags & INET_FRAG_COMPLETE)) { fq_unlink(fq, f); atomic_dec(&fq->refcnt); - fq->flags |= INET_FRAG_COMPLETE; } } EXPORT_SYMBOL(inet_frag_kill); @@ -328,11 +320,12 @@ void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f) fp = xp; } sum = sum_truesize + f->qsize; - sub_frag_mem_limit(q->net, sum); if (f->destructor) f->destructor(q); kmem_cache_free(f->frags_cachep, q); + + sub_frag_mem_limit(nf, sum); } EXPORT_SYMBOL(inet_frag_destroy);