Re: [dpdk-dev] [PATCH 2/2] event/sw: use dynamically-sized IQs

["Eads, Gage" <gage.eads@intel.com>]

Hi Pavan,

Thanks for the report and the GDB output. We've reproduced this and traced it down to how the PMD (mis)handles the re-configuration case. When the SW PMD is reconfigured, it reallocates the IQ chunks and reinitializes the chunk freelist, but it doesn't delete the stale pointers in sw->qids[*].iq. This causes multiple references to the same IQ memory to exist in the system, eventually resulting in the segfault.

I expect a proper fix will take us a day or two, but in the meantime the following change should fix the segfault ***for your specific usage only***:

diff --git a/drivers/event/sw/sw_evdev.c b/drivers/event/sw/sw_evdev.c
index 1ef6340..01da538 100644
--- a/drivers/event/sw/sw_evdev.c
+++ b/drivers/event/sw/sw_evdev.c
@@ -436,7 +436,7 @@ sw_dev_configure(const struct rte_eventdev *dev)
 
        /* If this is a reconfiguration, free the previous IQ allocation */
        if (sw->chunks)
-               rte_free(sw->chunks);
+               return 0;
 
        sw->chunks = rte_malloc_socket(NULL,
                                       sizeof(struct sw_queue_chunk) *

Mulling over the fix raises a question that the documentation is unclear on. If the user sends events into an eventdev, then calls rte_event_dev_stop() -> rte_event_dev_configure() -> rte_event_dev_start(), is the eventdev required to maintain any previously queued events? I would expect not. However, if the user calls calls rte_event_dev_stop() -> rte_event_queue_setup() -> rte_event_dev_start() (i.e. it is an additive reconfiguration), it seems more reasonable that the other event queues would maintain their contents. I'd imagine this is also hardware/device-dependent.

Thanks,
Gage

> -----Original Message-----
> From: Pavan Nikhilesh [mailto:pbhagavatula@caviumnetworks.com]
> Sent: Monday, January 8, 2018 10:06 AM
> To: Van Haaren, Harry <harry.van.haaren@intel.com>; Eads, Gage
> <gage.eads@intel.com>; jerin.jacob@caviumnetworks.com;
> santosh.shukla@caviumnetworks.com
> Cc: dev@dpdk.org
> Subject: Re: [PATCH 2/2] event/sw: use dynamically-sized IQs
> 
> On Mon, Jan 08, 2018 at 03:50:24PM +0000, Van Haaren, Harry wrote:
> > > From: Pavan Nikhilesh [mailto:pbhagavatula@caviumnetworks.com]
> > > Sent: Monday, January 8, 2018 3:32 PM
> > > To: Eads, Gage <gage.eads@intel.com>; Van Haaren, Harry
> > > <harry.van.haaren@intel.com>; jerin.jacob@caviumnetworks.com;
> > > santosh.shukla@caviumnetworks.com
> > > Cc: dev@dpdk.org
> > > Subject: Re: [PATCH 2/2] event/sw: use dynamically-sized IQs
> > >
> > > On Wed, Nov 29, 2017 at 09:08:34PM -0600, Gage Eads wrote:
> > > > This commit introduces dynamically-sized IQs, by switching the
> > > > underlying data structure from a fixed-size ring to a linked list of queue
> 'chunks.'
> >
> > <snip>
> >
> > > Sw eventdev crashes when used alongside Rx adapter. The crash
> > > happens when pumping traffic at > 1.4mpps. This commit seems responsible
> for this.
> > >
> > >
> > > Apply the following Rx adapter patch
> > > http://dpdk.org/dev/patchwork/patch/31977/
> > > Command used:
> > > ./build/eventdev_pipeline_sw_pmd -c 0xfffff8 --vdev="event_sw" --
> > > -r0x800
> > > -t0x100 -w F000 -e 0x10
> >
> > Applied the patch to current master, recompiled; cannot reproduce here..
> >
> master in the sense dpdk-next-eventdev right?
> > Is it 100% reproducible and "instant" or can it take some time to occur there?
> >
> It is instant
> >
> > > Backtrace:
> > >
> > > Thread 4 "lcore-slave-4" received signal SIGSEGV, Segmentation fault.
> > > [Switching to Thread 0xffffb6c8f040 (LWP 25291)]
> > > 0x0000aaaaaadcc0d4 in iq_dequeue_burst (count=48, ev=0xffffb6c8dd38,
> > > iq=0xffff9f764720, sw=0xffff9f332600) at
> > > /root/clean/rebase/dpdk-next-eventdev/drivers/event/sw/iq_chunk.h:14
> > > 2
> > > 142 ev[total++] = current->events[index++];
> >
> > Could we get the output of (gdb) info locals?
> >
> 
> Thread 4 "lcore-slave-4" received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0xffffb6c8f040 (LWP 19751)]
> 0x0000aaaaaadcc0d4 in iq_dequeue_burst (count=48, ev=0xffffb6c8dd38,
> iq=0xffff9f764620, sw=0xffff9f332500) at
> /root/clean/rebase/dpdk-next-eventdev/drivers/event/sw/iq_chunk.h:142
> 142 ev[total++] = current->events[index++];
> 
> (gdb) info locals
> next = 0x7000041400be73b
> current = 0x7000041400be73b
> total = 36
> index = 1
> (gdb)
> 
> 
> Noticed an other crash:
> 
> Thread 4 "lcore-slave-4" received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0xffffb6c8f040 (LWP 19690)]
> 0x0000aaaaaadcfb78 in iq_alloc_chunk (sw=0xffff9f332500) at
> /root/clean/rebase/dpdk-next-eventdev/drivers/event/sw/iq_chunk.h:63
> 63		sw->chunk_list_head = chunk->next;
> 
> (gdb) info locals
> chunk = 0x14340000119
> 
> (gdb) bt
> #0  0x0000aaaaaadcfb78 in iq_alloc_chunk (sw=0xffff9f332500) at
> /root/clean/rebase/dpdk-next-eventdev/drivers/event/sw/iq_chunk.h:63
> #1  iq_enqueue (ev=0xffff9f3967c0, iq=0xffff9f764620, sw=0xffff9f332500) at
> /root/clean/rebase/dpdk-next-eventdev/drivers/event/sw/iq_chunk.h:95
> #2  __pull_port_lb (allow_reorder=0, port_id=5, sw=0xffff9f332500) at
> /root/clean/rebase/dpdk-next-
> eventdev/drivers/event/sw/sw_evdev_scheduler.c:463
> #3  sw_schedule_pull_port_no_reorder (sw=0xffff9f332500, port_id=5) at
> /root/clean/rebase/dpdk-next-
> eventdev/drivers/event/sw/sw_evdev_scheduler.c:486
> #4  0x0000aaaaaadd0608 in sw_event_schedule (dev=0xaaaaaafbd200
> <rte_event_devices>) at
> /root/clean/rebase/dpdk-next-
> eventdev/drivers/event/sw/sw_evdev_scheduler.c:554
> #5  0x0000aaaaaadca008 in sw_sched_service_func (args=0xaaaaaafbd200
> <rte_event_devices>) at
> /root/clean/rebase/dpdk-next-eventdev/drivers/event/sw/sw_evdev.c:767
> #6  0x0000aaaaaab54740 in rte_service_runner_do_callback (s=0xffff9fffdf80,
> cs=0xffff9ffef900, service_idx=0) at
> /root/clean/rebase/dpdk-next-
> eventdev/lib/librte_eal/common/rte_service.c:349
> #7  0x0000aaaaaab54868 in service_run (i=0, cs=0xffff9ffef900,
> service_mask=18446744073709551615) at
> /root/clean/rebase/dpdk-next-
> eventdev/lib/librte_eal/common/rte_service.c:376
> #8  0x0000aaaaaab54954 in rte_service_run_iter_on_app_lcore (id=0,
> serialize_mt_unsafe=1) at
> /root/clean/rebase/dpdk-next-
> eventdev/lib/librte_eal/common/rte_service.c:405
> #9  0x0000aaaaaaaef04c in schedule_devices (lcore_id=4) at
> /root/clean/rebase/dpdk-next-
> eventdev/examples/eventdev_pipeline_sw_pmd/main.c:223
> #10 0x0000aaaaaaaef234 in worker (arg=0xffff9f331c80) at
> /root/clean/rebase/dpdk-next-
> eventdev/examples/eventdev_pipeline_sw_pmd/main.c:274
> #11 0x0000aaaaaab4382c in eal_thread_loop (arg=0x0) at
> /root/clean/rebase/dpdk-next-
> eventdev/lib/librte_eal/linuxapp/eal/eal_thread.c:182
> #12 0x0000ffffb7e46d64 in start_thread () from /usr/lib/libpthread.so.0
> #13 0x0000ffffb7da8bbc in thread_start () from /usr/lib/libc.so.6
> 
> 
> >
> >
> > > (gdb) bt
> > > #0  0x0000aaaaaadcc0d4 in iq_dequeue_burst (count=48,
> > > ev=0xffffb6c8dd38, iq=0xffff9f764720, sw=0xffff9f332600) at
> > > /root/clean/rebase/dpdk-next-eventdev/drivers/event/sw/iq_chunk.h:14
> > > 2
> > > #1  sw_schedule_atomic_to_cq (sw=0xffff9f332600, qid=0xffff9f764700,
> > > iq_num=0,
> > > count=48) at
> > > /root/clean/rebase/dpdk-next-
> > > eventdev/drivers/event/sw/sw_evdev_scheduler.c:74
> > > #2  0x0000aaaaaadcdc44 in sw_schedule_qid_to_cq (sw=0xffff9f332600)
> > > at
> > > /root/clean/rebase/dpdk-next-
> > > eventdev/drivers/event/sw/sw_evdev_scheduler.c:262
> > > #3  0x0000aaaaaadd069c in sw_event_schedule (dev=0xaaaaaafbd200
> > > <rte_event_devices>) at
> > > /root/clean/rebase/dpdk-next-
> > > eventdev/drivers/event/sw/sw_evdev_scheduler.c:564
> > > #4  0x0000aaaaaadca008 in sw_sched_service_func (args=0xaaaaaafbd200
> > > <rte_event_devices>) at
> > > /root/clean/rebase/dpdk-next-eventdev/drivers/event/sw/sw_evdev.c:76
> > > 7
> > > #5  0x0000aaaaaab54740 in rte_service_runner_do_callback
> > > (s=0xffff9fffdf80, cs=0xffff9ffef900, service_idx=0) at
> > > /root/clean/rebase/dpdk-next-
> > > eventdev/lib/librte_eal/common/rte_service.c:349
> > > #6  0x0000aaaaaab54868 in service_run (i=0, cs=0xffff9ffef900,
> > > service_mask=18446744073709551615) at
> > > /root/clean/rebase/dpdk-next-
> > > eventdev/lib/librte_eal/common/rte_service.c:376
> > > #7  0x0000aaaaaab54954 in rte_service_run_iter_on_app_lcore (id=0,
> > > serialize_mt_unsafe=1) at
> > > /root/clean/rebase/dpdk-next-
> > > eventdev/lib/librte_eal/common/rte_service.c:405
> > > #8  0x0000aaaaaaaef04c in schedule_devices (lcore_id=4) at
> > > /root/clean/rebase/dpdk-next-
> > > eventdev/examples/eventdev_pipeline_sw_pmd/main.c:223
> > > #9  0x0000aaaaaaaef234 in worker (arg=0xffff9f331d80) at
> > > /root/clean/rebase/dpdk-next-
> > > eventdev/examples/eventdev_pipeline_sw_pmd/main.c:274
> > > #10 0x0000aaaaaab4382c in eal_thread_loop (arg=0x0) at
> > > /root/clean/rebase/dpdk-next-
> > > eventdev/lib/librte_eal/linuxapp/eal/eal_thread.c:182
> > > #11 0x0000ffffb7e46d64 in start_thread () from
> > > /usr/lib/libpthread.so.0
> > > #12 0x0000ffffb7da8bbc in thread_start () from /usr/lib/libc.so.6
> > >
> > > Segfault seems to happen in sw_event_schedule and only happens under
> > > high traffic load.
> >
> > I've added -n 0 to the command line allowing it to run forever, and
> > after ~2 mins its still happily forwarding pkts at ~10G line rate here.
> >
> 
> On arm64 the crash is instant even without -n0.
> 
> >
> > > Thanks,
> > > Pavan
> >
> > Thanks for reporting - I'm afraid I'll have to ask a few questions to identify why
> I can't reproduce here before I can dig in and identify a fix.
> >
> > Anything special about the system that it is on?
> 
> Running on arm64 octeontx with 8x10G connected.
> 
> > What traffic pattern is being sent to the app?
> 
> Using something similar to trafficgen, IPv4/UDP pkts.
> 
>    0:00:51     958245 |0xB00   2816|0xB10   2832|0xB20   2848|0xB30
> 2864|0xC00 * 3072|0xC10 * 3088|0xC20 * 3104|0xC30 * 3120|    Totals
> Port Status           |XFI30     Up|XFI31     Up|XFI32     Up|XFI33     Up|XFI40
> Up|XFI41     Up|XFI42     Up|XFI43     Up|
>  1:Total TX packets   |  7197041566|  5194976604|  5120240981|  4424870160|
> 5860892739|  5191225514|  5126500427|  4429259828|42545007819
>  3:Total RX packets   |   358886055|   323055411|   321000948|   277179800|
> 387486466|   350278086|   348080242|   295460613|2661427621
>  6:TX packet rate     |           0|           0|           0|           0|           0|           0|           0|
> 0|         0
>  7:TX octet rate      |           0|           0|           0|           0|           0|           0|           0|
> 0|         0
>  8:TX bit rate, Mbps  |           0|           0|           0|           0|           0|           0|           0|
> 0|         0
> 10:RX packet rate     |           0|           0|           0|           0|           0|           0|           0|
> 0|         0
> 11:RX octet rate      |           0|           0|           0|           0|           0|           0|           0|
> 0|         0
> 12:RX bit rate, Mbps  |           0|           0|           0|           0|           0|           0|
> 0|           0|         0
> 36:tx.size            |          60|          60|          60|          60|          60|          60|          60|
> 60|
> 37:tx.type            |    IPv4+UDP|    IPv4+UDP|    IPv4+UDP|    IPv4+UDP|
> IPv4+UDP|    IPv4+UDP|    IPv4+UDP|    IPv4+UDP|
> 38:tx.payload         |         abc|         abc|         abc|         abc|         abc|         abc|
> abc|         abc|
> 47:dest.mac           |   fb71189c0|   fb71189d0|   fb71189e0|   fb71189bf|
> fb7118ac0|   fb7118ad0|   fb7118ae0|   fb7118abf|
> 51:src.mac            |   fb71189bf|   fb71189cf|   fb71189df|   fb71189ef|
> fb7118abf|   fb7118acf|   fb7118adf|   fb7118aef|
> 55:dest.ip            |   11.1.0.99|  11.17.0.99|  11.33.0.99|   11.0.0.99|   14.1.0.99|
> 14.17.0.99|  14.33.0.99|   14.0.0.99|
> 59:src.ip             |   11.0.0.99|  11.16.0.99|  11.32.0.99|  11.48.0.99|   14.0.0.99|
> 14.16.0.99|  14.32.0.99|  14.48.0.99|
> 73:bridge             |         off|         off|         off|         off|         off|         off|
> off|         off|
> 77:validate packets   |         off|         off|         off|         off|         off|         off|
> off|         off|
> 
> Thanks,
> Pavan.
> 
> >
> > Thanks
> >
> >
> > <snip>
> >