| Message ID | 20170320214848.13922.79201.stgit@localhost.localdomain |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
On Mon, 2017-03-20 at 14:48 -0700, Alexander Duyck wrote: > From: Alexander Duyck <alexander.h.duyck@intel.com> > > This patch is a cleanup/fix for NAPI IDs following the changes that made it > so that sender_cpu and napi_id were doing a better job of sharing the same > location in the sk_buff. > > One issue I found is that we weren't validating the napi_id as being valid > before we started trying to setup the busy polling. This change corrects > that by using the MIN_NAPI_ID value that is now used in both allocating the > NAPI IDs, as well as validating them. > > Fixes: 52bd2d62ce675 ("net: better skb->sender_cpu and skb->napi_id cohabitation") > Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com> > --- This Fixes: tag seems not really needed here. If really busy polling is attempted to a socket with a <wrong> napi id, nothing bad happens. This fits the advisory model of busy polling... Otherwise, your patch would be a candidate for net tree. Also note that as soon as sk_can_busy_loop(sk) returns some status, another cpu might already have changed sk->sk_napi_id to something else, possibly with a <wrong> napi id again. If your upcoming code depends on sk->sk_napi_id being verified, then you need to read it once.
diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h index c0452de83086..edf1310212a1 100644 --- a/include/net/busy_poll.h +++ b/include/net/busy_poll.h @@ -35,6 +35,12 @@ extern unsigned int sysctl_net_busy_read __read_mostly; extern unsigned int sysctl_net_busy_poll __read_mostly; +/* 0 - Reserved to indicate value not set + * 1..NR_CPUS - Reserved for sender_cpu + * NR_CPUS+1..~0 - Region available for NAPI IDs + */ +#define MIN_NAPI_ID ((unsigned int)(NR_CPUS + 1)) + static inline bool net_busy_loop_on(void) { return sysctl_net_busy_poll; @@ -58,10 +64,11 @@ static inline unsigned long busy_loop_end_time(void) static inline bool sk_can_busy_loop(const struct sock *sk) { - return sk->sk_ll_usec && sk->sk_napi_id && !signal_pending(current); + return sk->sk_ll_usec && + (sk->sk_napi_id >= MIN_NAPI_ID) && + !signal_pending(current); } - static inline bool busy_loop_timeout(unsigned long end_time) { unsigned long now = busy_loop_us_clock(); diff --git a/net/core/dev.c b/net/core/dev.c index 7869ae3837ca..5bbe30c08a5b 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -5143,10 +5143,10 @@ static void napi_hash_add(struct napi_struct *napi) spin_lock(&napi_hash_lock); - /* 0..NR_CPUS+1 range is reserved for sender_cpu use */ + /* 0..NR_CPUS range is reserved for sender_cpu use */ do { - if (unlikely(++napi_gen_id < NR_CPUS + 1)) - napi_gen_id = NR_CPUS + 1; + if (unlikely(++napi_gen_id < MIN_NAPI_ID)) + napi_gen_id = MIN_NAPI_ID; } while (napi_by_id(napi_gen_id)); napi->napi_id = napi_gen_id;