On Tue, Jun 22, 2021 at 01:51:24PM +0200, Frederic Weisbecker wrote:
On Tue, Jun 22, 2021 at 01:21:59PM +0200, Steffen Klassert wrote:
On Mon, Jun 21, 2021 at 01:05:28PM +0200, Steffen Klassert wrote:
On Mon, Jun 21, 2021 at 11:11:18AM +0200, Varad Gautam wrote:
Varad, can you try to replace the seqcount_mutex_t for xfrm_policy_hash_generation by a seqcount_spinlock_t? I'm not familiar with that seqcount changes, but we should not end up with using a mutex in this codepath.
Something like this? (beware, untested, also I don't know if the read side should then disable bh, doesn't look necessary for PREEMPT_RT, but I may be missing something...)
diff --git a/include/net/netns/xfrm.h b/include/net/netns/xfrm.h index e816b6a3ef2b..9b376b87bd54 100644 --- a/include/net/netns/xfrm.h +++ b/include/net/netns/xfrm.h @@ -74,6 +74,7 @@ struct netns_xfrm { #endif spinlock_t xfrm_state_lock; seqcount_spinlock_t xfrm_state_hash_generation;
- seqcount_spinlock_t xfrm_policy_hash_generation;
spinlock_t xfrm_policy_lock; struct mutex xfrm_cfg_mutex; diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index ce500f847b99..46a6d15b66d6 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -155,7 +155,6 @@ static struct xfrm_policy_afinfo const __rcu *xfrm_policy_afinfo[AF_INET6 + 1] __read_mostly; static struct kmem_cache *xfrm_dst_cache __ro_after_init; -static __read_mostly seqcount_mutex_t xfrm_policy_hash_generation; static struct rhashtable xfrm_policy_inexact_table; static const struct rhashtable_params xfrm_pol_inexact_params; @@ -585,7 +584,7 @@ static void xfrm_bydst_resize(struct net *net, int dir) return; spin_lock_bh(&net->xfrm.xfrm_policy_lock);
- write_seqcount_begin(&xfrm_policy_hash_generation);
- write_seqcount_begin(&net->xfrm.xfrm_policy_hash_generation);
odst = rcu_dereference_protected(net->xfrm.policy_bydst[dir].table, lockdep_is_held(&net->xfrm.xfrm_policy_lock)); @@ -596,7 +595,7 @@ static void xfrm_bydst_resize(struct net *net, int dir) rcu_assign_pointer(net->xfrm.policy_bydst[dir].table, ndst); net->xfrm.policy_bydst[dir].hmask = nhashmask;
- write_seqcount_end(&xfrm_policy_hash_generation);
- write_seqcount_end(&net->xfrm.xfrm_policy_hash_generation); spin_unlock_bh(&net->xfrm.xfrm_policy_lock);
synchronize_rcu(); @@ -1245,7 +1244,7 @@ static void xfrm_hash_rebuild(struct work_struct *work) } while (read_seqretry(&net->xfrm.policy_hthresh.lock, seq)); spin_lock_bh(&net->xfrm.xfrm_policy_lock);
- write_seqcount_begin(&xfrm_policy_hash_generation);
- write_seqcount_begin(&net->xfrm.xfrm_policy_hash_generation);
/* make sure that we can insert the indirect policies again before * we start with destructive action. @@ -1354,7 +1353,7 @@ static void xfrm_hash_rebuild(struct work_struct *work) out_unlock: __xfrm_policy_inexact_flush(net);
- write_seqcount_end(&xfrm_policy_hash_generation);
- write_seqcount_end(&net->xfrm.xfrm_policy_hash_generation); spin_unlock_bh(&net->xfrm.xfrm_policy_lock);
mutex_unlock(&hash_resize_mutex); @@ -2095,9 +2094,9 @@ static struct xfrm_policy *xfrm_policy_lookup_bytype(struct net *net, u8 type, rcu_read_lock(); retry: do {
sequence = read_seqcount_begin(&xfrm_policy_hash_generation);
sequence = read_seqcount_begin(&net->xfrm.xfrm_policy_hash_generation);
- } while (read_seqcount_retry(&xfrm_policy_hash_generation, sequence));
- } while (read_seqcount_retry(&net->xfrm.xfrm_policy_hash_generation, sequence));
ret = NULL; hlist_for_each_entry_rcu(pol, chain, bydst) { @@ -2128,7 +2127,7 @@ static struct xfrm_policy *xfrm_policy_lookup_bytype(struct net *net, u8 type, } skip_inexact:
- if (read_seqcount_retry(&xfrm_policy_hash_generation, sequence))
- if (read_seqcount_retry(&net->xfrm.xfrm_policy_hash_generation, sequence)) goto retry;
if (ret && !xfrm_pol_hold_rcu(ret)) @@ -4084,6 +4083,7 @@ static int __net_init xfrm_net_init(struct net *net) /* Initialize the per-net locks here */ spin_lock_init(&net->xfrm.xfrm_state_lock); spin_lock_init(&net->xfrm.xfrm_policy_lock);
- seqcount_spinlock_init(&net->xfrm.xfrm_policy_hash_generation, &net->xfrm.xfrm_policy_lock); mutex_init(&net->xfrm.xfrm_cfg_mutex);
rv = xfrm_statistics_init(net); @@ -4128,7 +4128,6 @@ void __init xfrm_init(void) { register_pernet_subsys(&xfrm_net_ops); xfrm_dev_init();
- seqcount_mutex_init(&xfrm_policy_hash_generation, &hash_resize_mutex); xfrm_input_init();
#ifdef CONFIG_XFRM_ESPINTCP
Yes, looks like your patch should do it. The xfrm_policy_lock is the write side protection for the seqcount here.
Thanks!