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Date: Mon, 28 Sep 2020 09:44:36 -0700 From: "Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@...el.com> To: Sinan Kaya <okaya@...nel.org>, "Zhao, Haifeng" <haifeng.zhao@...el.com>, "bhelgaas@...gle.com" <bhelgaas@...gle.com>, "oohall@...il.com" <oohall@...il.com>, "ruscur@...sell.cc" <ruscur@...sell.cc>, "lukas@...ner.de" <lukas@...ner.de>, "andriy.shevchenko@...ux.intel.com" <andriy.shevchenko@...ux.intel.com>, "stuart.w.hayes@...il.com" <stuart.w.hayes@...il.com>, "mr.nuke.me@...il.com" <mr.nuke.me@...il.com>, "mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>, Keith Busch <keith.busch@...el.com> Cc: "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Jia, Pei P" <pei.p.jia@...el.com>, "ashok.raj@...ux.intel.com" <ashok.raj@...ux.intel.com> Subject: Re: [PATCH 2/5 V2] PCI: pciehp: check and wait port status out of DPC before handling DLLSC and PDC On 9/28/20 9:43 AM, Sinan Kaya wrote: > On 9/28/2020 7:10 AM, Sinan Kaya wrote: >> On 9/27/2020 10:01 PM, Zhao, Haifeng wrote: >>> Sinan, >>> I explained the reason why locks don't protect this case in the patch description part. >>> Write side and read side hold different semaphore and mutex. >>> >> I have been thinking about it some time but is there any reason why we >> have to handle all port AER/DPC/HP events in different threads? >> >> Can we go to single threaded event loop for all port drivers events? >> >> This will require some refactoring but it wlll eliminate the lock >> nightmares we are having. >> >> This means no sleeping. All sleeps need to happen outside of the loop. >> >> I wanted to see what you all are thinking about this. >> >> It might become a performance problem if the system is >> continuously observing a hotplug/aer/dpc events. >> >> I always think that these should be rare events. > If restructuring would be too costly, the preferred solution should be > to fix the locks in hotplug driver rather than throwing there a random > wait call. Since the current race condition is detected between DPC and hotplug, I recommend synchronizing them. -- Sathyanarayanan Kuppuswamy Linux Kernel Developer
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