Re: [dpdk-dev] [PATCH] eal: initialize alarms early

["Stojaczyk, Dariusz" <dariusz.stojaczyk@intel.com>]

> -----Original Message-----
> From: Stojaczyk, Dariusz
> Sent: Wednesday, March 27, 2019 9:34 PM
> To: Thomas Monjalon <thomas@monjalon.net>
> Cc: dev@dpdk.org; Zhang, Qi Z <qi.z.zhang@intel.com>; Burakov, Anatoly
> <anatoly.burakov@intel.com>; stable@dpdk.org
> Subject: RE: [dpdk-dev] [PATCH] eal: initialize alarms early
> 
> 
> 
> > -----Original Message-----
> > From: Thomas Monjalon [mailto:thomas@monjalon.net]
> > Sent: Wednesday, March 27, 2019 7:12 PM
> > To: Stojaczyk, Dariusz <dariusz.stojaczyk@intel.com>
> > Cc: dev@dpdk.org; Zhang, Qi Z <qi.z.zhang@intel.com>; Burakov, Anatoly
> > <anatoly.burakov@intel.com>; stable@dpdk.org
> > Subject: Re: [dpdk-dev] [PATCH] eal: initialize alarms early
> >
> > 26/03/2019 19:43, Darek Stojaczyk:
> > > We currently initialize rte_alarms after starting
> > > to listen for IPC hotplug requests, which gives
> > > us a data race window. Upon receiving such hotplug
> > > request we always try to set an alarm and this
> > > obviously doesn't work if the alarms weren't
> > > initialized yet.
> > >
> > > To fix it, we initialize alarms before starting
> > > to listen for IPC hotplug messages. Specifically,
> > > we move rte_eal_alarm_init() right after
> > > rte_eal_intr_init() as it makes some sense to
> > > keep those two close to each other.
> >
> > I wonder which regression it will bring :)
> > The experience shows that we cannot touch this function
> > without introducing a regression. Please check twice.
> 
> Hah, ok - I'll check again the possible outcomes of this.
> 

Done, I can't see any case I could break.

> >
> > > Fixes: 244d5130719c ("eal: enable hotplug on multi-process")
> > > Cc: Qi Zhang <qi.z.zhang@intel.com>
> > > Cc: Anatoly Burakov <anatoly.burakov@intel.com>
> > > Cc: stable@dpdk.org
> > >
> > > Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
> > > ---
> > >  lib/librte_eal/linux/eal/eal.c | 12 ++++++------
> > >  1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > You probably need to update the FreeBSD version too.
> >
> 
> Oh, that I cannot do. First of all, in bsd code I don't see
> rte_mp_dev_hotplug_init() called anywhere, as if bsd
> did not listen for IPC hotplug messages at all and hence did
> not have any data race in this area. Second, I would be
> afraid to touch any bsd code as I'm not running any bsd
> system.

Basing on Anatoly's feedback, I pushed a v2 with bsd changes
included as well.

Thanks!
D.

> 
> D.