Hi Hanoch, Please find some comments below.
On 12/27/2015 10:39 AM, Hanoch Haim (hhaim) wrote: > Hi Bruce, > > I'm Hanoch from Cisco Systems works for the > https://github.com/cisco-system-traffic-generator/trex-core traffic generator > project. > > While upgrading from DPDK 1.8 to 2.2 Ido found that the following commit > creates a mbuf corruption and result in Tx hang > > > > commit f20b50b946da9070d21e392e4dbc7d9f68bc983e > > Author: Olivier Matz <olivier.matz at 6wind.com> > > Date: Mon Jun 8 16:57:22 2015 +0200 > > > > Looking at the change it is clear why there is an issue, wanted to get your > input. > > > > Init > > ----- > > alloc const mbuf ==> mbuf-a (ref=1) > > > > Simple case that works > > --------------------- > > > > thread 1 , tx: alloc-mbuf->attach(mbuf-a) (ref=2) inc- non atomic > > thread 1 , tx: alloc-mbuf->attach(mbuf-a) (ref32) inc- atomic do you mean "(ref=3)" ? > > thread 1 , drv : free() (ref=2) dec- atomic > > thread 1 , drv : free() (ref=3) dec - non atomic do you mean "(ref=1)" ? > > Simple case that does not work > > --------------------- > > > > Both do that in parallel > > > > thread 2 tx : alloc-mbuf->attach(mbuf-a) (ref=2) inc- non atomic > > thread 1 tx : alloc-mbuf->attach(mbuf-a) (ref=2) inc- non atomic It is not allowed to call a function from the mbuf API in parallel. Example: core0 | core1 --------------------------------|--------------------------------------- m = rte_pktmbuf_alloc(m); | enqueue(m); | |m = dequeue(); do_something(m); |do_something(m); do_something() is not allowed because it accesses the same mbuf structure. do_something() can be any function of mbuf API: rte_pktmbuf_prepend(), rte_pktmbuf_attach(), ... This is allowed: core0 | core1 --------------------------------|--------------------------------------- m = rte_pktmbuf_alloc(m); | m2 = rte_pktmbuf_attach(m); | enqueue(m2); | |m2 = dequeue(); do_something(m); |do_something(m2); Regards, Olivier
