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net: Busy polling should ignore sender CPUs 

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.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexander Duyck 2017-03-24 10:07:53 -07:00 committed by David S. Miller
parent dcb421f427
commit 545cd5e5ec
2 changed files with 16 additions and 6 deletions
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9
include/net/busy_poll.h
View File

@ -35,6 +35,12 @@ struct napi_struct;
extern unsigned int sysctl_net_busy_read __read_mostly; extern unsigned int sysctl_net_busy_read __read_mostly;
extern unsigned int sysctl_net_busy_poll __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) static inline bool net_busy_loop_on(void)
{ {
return sysctl_net_busy_poll; return sysctl_net_busy_poll;
@ -58,10 +64,9 @@ static inline unsigned long busy_loop_end_time(void)
static inline bool sk_can_busy_loop(const struct sock *sk) 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 && !signal_pending(current);
} }
static inline bool busy_loop_timeout(unsigned long end_time) static inline bool busy_loop_timeout(unsigned long end_time)
{ {
unsigned long now = busy_loop_us_clock(); unsigned long now = busy_loop_us_clock();

13
net/core/dev.c
View File

@ -5066,15 +5066,20 @@ bool sk_busy_loop(struct sock *sk, int nonblock)
int (*napi_poll)(struct napi_struct *napi, int budget); int (*napi_poll)(struct napi_struct *napi, int budget);
void *have_poll_lock = NULL; void *have_poll_lock = NULL;
struct napi_struct *napi; struct napi_struct *napi;
unsigned int napi_id;
int rc; int rc;
restart: restart:
napi_id = READ_ONCE(sk->sk_napi_id);
if (napi_id < MIN_NAPI_ID)
return 0;
rc = false; rc = false;
napi_poll = NULL; napi_poll = NULL;
rcu_read_lock(); rcu_read_lock();
napi = napi_by_id(sk->sk_napi_id); napi = napi_by_id(napi_id);
if (!napi) if (!napi)
goto out; goto out;
@ -5143,10 +5148,10 @@ static void napi_hash_add(struct napi_struct *napi)
spin_lock(&napi_hash_lock); 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 { do {
if (unlikely(++napi_gen_id < NR_CPUS + 1)) if (unlikely(++napi_gen_id < MIN_NAPI_ID))
napi_gen_id = NR_CPUS + 1; napi_gen_id = MIN_NAPI_ID;
} while (napi_by_id(napi_gen_id)); } while (napi_by_id(napi_gen_id));
napi->napi_id = napi_gen_id; napi->napi_id = napi_gen_id;