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From: Tal Shnaiderman <talshn@nvidia.com>
To: Dmitry Malloy <dmitrym@microsoft.com>,
	Narcisa Ana Maria Vasile <Narcisa.Vasile@microsoft.com>
Cc: NBU-Contact-Thomas Monjalon <thomas@monjalon.net>,
	"Narcisa Ana Maria Vasile" <navasile@linux.microsoft.com>,
	Pallavi Kadam <pallavi.kadam@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>,
	Suanming Mou <suanmingm@nvidia.com>
Subject: Re: [dpdk-dev] [PATCH v3 1/2] eal/windows: add pthread mutex lock
Date: Wed, 14 Oct 2020 10:02:16 +0000
Message-ID: <BYAPR12MB3285A0E85589C37EC0C534DFA4050@BYAPR12MB3285.namprd12.prod.outlook.com> (raw)
In-Reply-To: <MWHPR12MB17436632393C15AD81E08086C10B0@MWHPR12MB1743.namprd12.prod.outlook.com>

Hi DmitryM, Naty,

We would like to know if the macro added below for PTHREAD_MUTEX_INITIALIZER is a safe initialization of a CRITICAL_SECTION.

Can you please review the code and explanation below and check it internally?  

> Subject: Re: [dpdk-dev] [PATCH v3 1/2] eal/windows: add pthread mutex
> lock
> 
> External email: Use caution opening links or attachments
> 
> 
> Hi Dmitry,
> 
> Thank you very much.
> I also got some messages that they wish the PTHREAD_MUTEX_INITIALIZER
> macro can also be supported.
> 
> Refer to [1], we found that with critical section solution, maybe the macro
> can be defined as this:
> #define PTHREAD_MUTEX_INITIALIZER {(void*)-1,-1,0,0,0,0}
> 
> We have tested that works, so I would prefer to add that if the macro is also
> OK with you.
> What do you think about that?
> 
> The explanation from [1]:
> " The pthreads API has an initialization macro that has no correspondence to
> anything in the windows API. By investigating the internal definition of the
> critical section type, one may work out how to initialize one without calling
> InitializeCriticalSection(). The trick here is that InitializeCriticalSection() is not
> allowed to fail. It tries to allocate a critical section debug object, but if no
> memory is available, it sets the pointer to a specific value. (One would expect
> that value to be NULL, but it is actually (void *)-1 for some reason.) Thus we
> can use this special value for that pointer, and the critical section code will
> work.
> 
> The other important part of the critical section type to initialize is the number
> of waiters. This controls whether or not the mutex is locked. Fortunately, this
> part of the critical section is unlikely to change. Apparently, many programs
> already test critical sections to see if they are locked using this value, so
> Microsoft felt that it was necessary to keep it set at -1 for an unlocked critical
> section, even when they changed the underlying algorithm to be more
> scalable. The final parts of the critical section object are unimportant, and can
> be set to zero for their defaults."
> 
> [1]
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flockl
> essinc.com%2Farticles%2Fpthreads_on_windows%2F&amp;data=02%7C01%
> 7Ctalshn%40nvidia.com%7C4533970f5c964751eeea08d86b3483e3%7C43083d
> 15727340c1b7db39efd9ccc17a%7C0%7C0%7C637377220576713708&amp;sdat
> a=qELFpXSw7%2Fk8m9FMIidiQsnTq%2BeyJRII8C1sDyrHJe4%3D&amp;reserv
> ed=0
> 
> BR,
> SuanmingMou
> 
> > -----Original Message-----
> > From: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
> > Sent: Thursday, October 8, 2020 12:54 AM
> > To: Suanming Mou <suanmingm@nvidia.com>
> > Cc: Narcisa Ana Maria Vasile <navasile@linux.microsoft.com>; Dmitry
> > Malloy <dmitrym@microsoft.com>; Pallavi Kadam
> > <pallavi.kadam@intel.com>; dev@dpdk.org
> > Subject: Re: [PATCH v3 1/2] eal/windows: add pthread mutex lock
> >
> > On Wed,  7 Oct 2020 22:17:28 +0800, Suanming Mou wrote:
> > > Add pthread mutex lock as it is needed for the thread safe rte_flow
> > > functions.
> > >
> > > Signed-off-by: Suanming Mou <suanmingm@nvidia.com>
> >
> > Acked-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>

  reply	other threads:[~2020-10-14 10:03 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-27  8:20 [dpdk-dev] [PATCH 0/2] ethdev: make rte flow API thread safe Suanming Mou
2020-09-27  8:20 ` [dpdk-dev] [PATCH 1/2] eal/windows: add pthread mutex lock Suanming Mou
2020-09-27 15:56   ` Dmitry Kozlyuk
2020-09-28  2:30     ` Suanming Mou
2020-09-27  8:20 ` [dpdk-dev] [PATCH 2/2] ethdev: make rte flow API thread safe Suanming Mou
2020-09-30 10:56   ` Ori Kam
2020-10-04 23:44     ` Suanming Mou
2020-10-04 23:48 ` [dpdk-dev] [PATCH v2 0/2] ethdev: make rte_flow " Suanming Mou
2020-10-04 23:48   ` [dpdk-dev] [PATCH v2 1/2] eal/windows: add pthread mutex lock Suanming Mou
2020-10-04 23:48   ` [dpdk-dev] [PATCH v2 2/2] ethdev: make rte_flow API thread safe Suanming Mou
2020-10-05 11:28     ` Ori Kam
2020-10-06 23:18       ` Ajit Khaparde
2020-10-07  0:50         ` Suanming Mou
2020-10-07  6:33           ` Ori Kam
2020-10-07 14:17 ` [dpdk-dev] [PATCH v3 0/2] " Suanming Mou
2020-10-07 14:17   ` [dpdk-dev] [PATCH v3 1/2] eal/windows: add pthread mutex lock Suanming Mou
2020-10-07 16:53     ` Dmitry Kozlyuk
2020-10-08  2:46       ` Suanming Mou
2020-10-14 10:02         ` Tal Shnaiderman [this message]
2020-10-07 14:17   ` [dpdk-dev] [PATCH v3 2/2] ethdev: make rte_flow API thread safe Suanming Mou
2020-10-07 14:42     ` Ajit Khaparde
2020-10-07 16:37       ` Ori Kam
2020-10-07 20:10     ` Matan Azrad
2020-10-08  2:56       ` Suanming Mou
2020-10-09  1:17 ` [dpdk-dev] [PATCH v4 0/2] " Suanming Mou
2020-10-09  1:17   ` [dpdk-dev] [PATCH v4 1/2] eal/windows: add pthread mutex lock Suanming Mou
2020-10-09  9:19     ` Tal Shnaiderman
2020-10-14 16:45     ` Ranjit Menon
2020-10-15  2:15     ` Narcisa Ana Maria Vasile
2020-10-15  2:18       ` Suanming Mou
2020-10-09  1:17   ` [dpdk-dev] [PATCH v4 2/2] ethdev: make rte_flow API thread safe Suanming Mou
2020-10-14 10:19     ` Thomas Monjalon
2020-10-14 10:41       ` Suanming Mou
2020-10-15  1:07 ` [dpdk-dev] [PATCH v5 0/2] " Suanming Mou
2020-10-15  1:07   ` [dpdk-dev] [PATCH v5 1/2] eal/windows: add pthread mutex lock Suanming Mou
2020-10-15  2:22     ` Narcisa Ana Maria Vasile
2020-10-15  1:07   ` [dpdk-dev] [PATCH v5 2/2] ethdev: make rte_flow API thread safe Suanming Mou
2020-10-15  8:28     ` Thomas Monjalon
2020-10-15  8:52       ` Andrew Rybchenko
2020-10-15 22:43   ` [dpdk-dev] [PATCH v5 0/2] " Thomas Monjalon

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