Re: [dpdk-dev] [PATCH] eal: fix threads block on barrier

[Shreyansh Jain <shreyansh.jain@nxp.com>]

> -----Original Message-----
> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> Sent: Friday, April 27, 2018 11:10 PM
> To: Shreyansh Jain <shreyansh.jain@nxp.com>
> Cc: Jianfeng Tan <jianfeng.tan@intel.com>; dev@dpdk.org;
> thomas@monjalon.net; Olivier Matz <olivier.matz@6wind.com>; Anatoly
> Burakov <anatoly.burakov@intel.com>
> Subject: Re: [dpdk-dev] [PATCH] eal: fix threads block on barrier
> 
> On Fri, 27 Apr 2018 17:36:56 +0000
> Shreyansh Jain <shreyansh.jain@nxp.com> wrote:
> 
> > > -----Original Message-----
> > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Jianfeng Tan
> > > Sent: Friday, April 27, 2018 10:12 PM
> > > To: dev@dpdk.org
> > > Cc: thomas@monjalon.net; Jianfeng Tan <jianfeng.tan@intel.com>;
> Olivier
> > > Matz <olivier.matz@6wind.com>; Anatoly Burakov
> > > <anatoly.burakov@intel.com>
> > > Subject: [dpdk-dev] [PATCH] eal: fix threads block on barrier
> > >
> > > Below commit introduced pthread barrier for synchronization.
> > > But two IPC threads block on the barrier, and never wake up.
> > >
> > >   (gdb) bt
> > >   #0  futex_wait (private=0, expected=0, futex_word=0x7fffffffcff4)
> > >       at ../sysdeps/unix/sysv/linux/futex-internal.h:61
> > >   #1  futex_wait_simple (private=0, expected=0,
> > > futex_word=0x7fffffffcff4)
> > >       at ../sysdeps/nptl/futex-internal.h:135
> > >   #2  __pthread_barrier_wait (barrier=0x7fffffffcff0) at
> > > pthread_barrier_wait.c:184
> > >   #3  rte_thread_init (arg=0x7fffffffcfe0)
> > >       at ../dpdk/lib/librte_eal/common/eal_common_thread.c:160
> > >   #4  start_thread (arg=0x7ffff6ecf700) at pthread_create.c:333
> > >   #5  clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
> > >
> > > Through analysis, we find the barrier defined on the stack could be
> the
> > > root cause. This patch will change to use heap memory as the
> barrier.
> > >
> > > Fixes: d651ee4919cd ("eal: set affinity for control threads")
> > >
> > > Cc: Olivier Matz <olivier.matz@6wind.com>
> > > Cc: Anatoly Burakov <anatoly.burakov@intel.com>
> > >
> > > Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
> >
> > Though I have seen Stephen's comment on this (possibly a library
> bug), this at least fixes an issue which was dogging dpaa and dpaa2 -
> generating bus errors and futex errors with variation in core masks
> provided to applications.
> >
> > Thanks a lot for this.
> >
> > Acked-by: Shreyansh Jain <shreyansh.jain@nxp.com>
> 
> Could you verify there is not a use after free by using valgrind or
> some library that poisons memory on free.

I will probably do that soon - but for the time being I don't want this issue to block the dpaa/dpaa2 for RC1 - these drivers were completely unusable without this patch.