From 822d54b9c2c18271239ad7d928f1e9c702676592 Mon Sep 17 00:00:00 2001 From: Alexander Duyck Date: Mon, 28 Sep 2015 09:16:17 -0700 Subject: netpoll: Drop budget parameter from NAPI polling call hierarchy For some reason we were carrying the budget value around between the various calls to napi->poll. If for example one of the drivers called had a bug in which it returned a non-zero value for work this could result in the budget value becoming negative. Rather than carry around a value of budget that is 0 or less we can instead just loop through and pass 0 to each napi->poll call. If any driver returns a value for work done that is non-zero then we can report that driver and continue rather than allowing a bad actor to make the budget value negative and pass that negative value to napi->poll. Note, the only actual change here is that instead of letting budget become negative we are keeping it at 0 regardless of the value returned for work since it should not be possible for the polling routine to do any actual work with a budget of 0. So if the polling routine returns a non-0 value we are just reporting it and continuing with a budget of 0 rather than letting that work value be subtracted from the budget of 0. Signed-off-by: Alexander Duyck Signed-off-by: David S. Miller --- net/core/netpoll.c | 23 +++++++++++------------ 1 file changed, 11 insertions(+), 12 deletions(-) (limited to 'net/core') diff --git a/net/core/netpoll.c b/net/core/netpoll.c index 8bdada242a7d..94acfc89ad97 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -140,7 +140,7 @@ static void queue_process(struct work_struct *work) * case. Further, we test the poll_owner to avoid recursion on UP * systems where the lock doesn't exist. */ -static int poll_one_napi(struct napi_struct *napi, int budget) +static void poll_one_napi(struct napi_struct *napi) { int work = 0; @@ -149,33 +149,33 @@ static int poll_one_napi(struct napi_struct *napi, int budget) * holding the napi->poll_lock. */ if (!test_bit(NAPI_STATE_SCHED, &napi->state)) - return budget; + return; /* If we set this bit but see that it has already been set, * that indicates that napi has been disabled and we need * to abort this operation */ if (test_and_set_bit(NAPI_STATE_NPSVC, &napi->state)) - goto out; + return; - work = napi->poll(napi, budget); - WARN_ONCE(work > budget, "%pF exceeded budget in poll\n", napi->poll); + /* We explicilty pass the polling call a budget of 0 to + * indicate that we are clearing the Tx path only. + */ + work = napi->poll(napi, 0); + WARN_ONCE(work, "%pF exceeded budget in poll\n", napi->poll); trace_napi_poll(napi); clear_bit(NAPI_STATE_NPSVC, &napi->state); - -out: - return budget - work; } -static void poll_napi(struct net_device *dev, int budget) +static void poll_napi(struct net_device *dev) { struct napi_struct *napi; list_for_each_entry(napi, &dev->napi_list, dev_list) { if (napi->poll_owner != smp_processor_id() && spin_trylock(&napi->poll_lock)) { - budget = poll_one_napi(napi, budget); + poll_one_napi(napi); spin_unlock(&napi->poll_lock); } } @@ -185,7 +185,6 @@ static void netpoll_poll_dev(struct net_device *dev) { const struct net_device_ops *ops; struct netpoll_info *ni = rcu_dereference_bh(dev->npinfo); - int budget = 0; /* Don't do any rx activity if the dev_lock mutex is held * the dev_open/close paths use this to block netpoll activity @@ -208,7 +207,7 @@ static void netpoll_poll_dev(struct net_device *dev) /* Process pending work on NIC */ ops->ndo_poll_controller(dev); - poll_napi(dev, budget); + poll_napi(dev); up(&ni->dev_lock); -- cgit v1.2.3-59-g8ed1b