path: root/net
diff options
authorAlexander Duyck <aduyck@mirantis.com>2015-09-28 09:16:17 -0700
committerDavid S. Miller <davem@davemloft.net>2015-09-29 14:57:16 -0700
commit822d54b9c2c18271239ad7d928f1e9c702676592 (patch)
tree5cbe32bb53daf8660e890a32fbdf06820ad5e029 /net
parentbridge: vlan: add per-vlan struct and move to rhashtables (diff)
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 <aduyck@mirantis.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
1 files changed, 11 insertions, 12 deletions
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);
clear_bit(NAPI_STATE_NPSVC, &napi->state);
- 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);
@@ -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 */
- poll_napi(dev, budget);
+ poll_napi(dev);