RE: [PATCH v3] raw/ifpga: fix pthread cannot join

["Zhang, Tianfei" <tianfei.zhang@intel.com>]

> -----Original Message-----
> From: Stephen Hemminger <stephen@networkplumber.org>
> Sent: Thursday, January 20, 2022 11:47 PM
> To: Huang, Wei <wei.huang@intel.com>
> Cc: dev@dpdk.org; Xu, Rosen <rosen.xu@intel.com>; Zhang, Qi Z
> <qi.z.zhang@intel.com>; stable@dpdk.org; Zhang, Tianfei
> <tianfei.zhang@intel.com>; Yigit, Ferruh <ferruh.yigit@intel.com>
> Subject: Re: [PATCH v3] raw/ifpga: fix pthread cannot join
> 
> On Thu, 20 Jan 2022 00:58:14 -0500
> Wei Huang <wei.huang@intel.com> wrote:
> 
> > diff --git a/drivers/raw/ifpga/ifpga_rawdev.c
> > b/drivers/raw/ifpga/ifpga_rawdev.c
> > index 8d9db58..2bc569b 100644
> > --- a/drivers/raw/ifpga/ifpga_rawdev.c
> > +++ b/drivers/raw/ifpga/ifpga_rawdev.c
> > @@ -497,7 +497,7 @@ static int set_surprise_link_check_aer(
> >  	int gsd_enable, ret;
> >  #define MS 1000
> >
> > -	while (1) {
> > +	while (ifpga_monitor_start) {
> 
> This will work on x86 CPU but not on CPU's with weak memory ordering like
> ARM.
> 
> You need to use atomic_builtin when accessing a flag shared between threads
> that is not being protected by a lock.

We submitted a v5 patch for your suggestion, but got a " coding style issues" which said that: 
Warning in drivers/raw/ifpga/ifpga_rawdev.c:
Using rte_atomicNN_xxx

We look at the devtools/checkpatches.sh script, it mentioned that rte_atomic APIs are forbidden.

ifpga_monitor_start just a flags to enable and disable the threads not share with threads. When the driver init it will start the thread, 
when the driver remove it want to stop the thread. I don't think it will has a concurrency issue on this scenario.