| Message ID | 21d3b5e617ed44d217ce7f82e9fafa06.squirrel@www.codeaurora.org |
|---|---|
| State | Rejected, archived |
| Delegated to: | David Miller |
| Headers | show |
On Mon, 2015-06-15 at 21:46 +0000, subashab@codeaurora.org wrote: > When NAPI_STATE_SCHED state is not set, enqueue_to_backlog() > will queue an IPI and add the backlog queue to the poll list. A packet > added by RPS onto the core could also add the NAPI backlog struct to the > poll list. This double addition to the list causes a crash - > > 2920.540304: <2> list_add double add: new=ffffffc076ed2930, > prev=ffffffc076ed2930, next=ffffffc076ed2850. > [<ffffffc000460dd4>] __list_add+0xcc/0xf0 > 2921.064962: <2> [<ffffffc000b44880>] rps_trigger_softirq+0x1c/0x40 > 2921.070779: <2> [<ffffffc000284a14>] > generic_smp_call_function_single_interrupt+0xe8/0x12c > 2921.078678: <2> [<ffffffc00020d9ac>] handle_IPI+0x8c/0x1ec > 2921.083796: <2> [<ffffffc000200714>] gic_handle_irq+0x94/0xb0 > > Fix this race for double addition to list by checking the NAPI state. > > Acked-by: Sharat Masetty <smasetty@qti.qualcomm.com> > Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org> > > diff --git a/net/core/dev.c b/net/core/dev.c > index 6f561de..57d6d39 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -3225,7 +3225,8 @@ static void rps_trigger_softirq(void *data) > { > struct softnet_data *sd = data; > > - ____napi_schedule(sd, &sd->backlog); > + if (!test_bit(NAPI_STATE_SCHED, &sd->backlog.state)) > + ____napi_schedule(sd, &sd->backlog); > sd->received_rps++; > } > I can not believe how many times you tried to send RPS patches. I do not see how this condition triggers. This code path is run billions of time per ms on our hosts and never got a single crash. Please describe where is the race condition you want to fix. Your test is racy by definition. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/core/dev.c b/net/core/dev.c index 6f561de..57d6d39 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3225,7 +3225,8 @@ static void rps_trigger_softirq(void *data) { struct softnet_data *sd = data; - ____napi_schedule(sd, &sd->backlog); + if (!test_bit(NAPI_STATE_SCHED, &sd->backlog.state)) + ____napi_schedule(sd, &sd->backlog); sd->received_rps++; }