From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Shevchenko Subject: Re: [PATCH v1 1/5] drivercore: Revert "deferral race condition fix" Date: Sat, 10 Nov 2018 20:36:29 +0200 Message-ID: <20181110183629.GE10650@smile.fi.intel.com> References: <20181110181101.24557-1-andriy.shevchenko@linux.intel.com> <20181110182622.GA32657@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20181110182622.GA32657@kroah.com> Sender: linux-kernel-owner@vger.kernel.org To: Greg Kroah-Hartman Cc: MyungJoo Ham , Chanwoo Choi , linux-usb@vger.kernel.org, Felipe Balbi , Guenter Roeck , Heikki Krogerus , Roger Quadros , linux-pm@vger.kernel.org, "Rafael J. Wysocki" , Sebastian Reichel , linux-omap@vger.kernel.org, Darren Hart , platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org, Chen-Yu Tsai , Hans de Goede , Grant Likely , Peter Ujfalusi , Mark Brown , Andrzej Hajda List-Id: linux-omap@vger.kernel.org On Sat, Nov 10, 2018 at 10:26:22AM -0800, Greg Kroah-Hartman wrote: > On Sat, Nov 10, 2018 at 08:10:57PM +0200, Andy Shevchenko wrote: > > Consider the following scenario. > > > > There are two independent devices coupled together by functional dependencies: > > - USB OTG (dwc3-pci) > > - extcon (tested with extcon-intel-mrfld, not yet in upstream) > > > > Each of the driver services a corresponding device is built as a module. In the > > Buildroot environment the modules are probed by alphabetical ordering of their > > modaliases. The latter comes to the case when USB OTG driver will be probed > > first followed by extcon one. > > > > So, if the platform anticipates extcon device to be appeared, in the above case > > we will get deferred probe of USB OTG, because of ordering. > > > > Now, a cherry on top of the cake, the deferred probing list contains > > the only two modules, i.e. USB OTG and extcon. Due to above circumstances, > > values in the local_trigger_count and deferred_trigger_count are not the same, > > and thus provokes deferred probe triggering again and again. > > > > ... > > [ 20.678332] platform dwc3.0.auto: Retrying from deferred list > > [ 20.694743] platform dwc3.0.auto: Driver dwc3 requests probe deferral > > [ 20.701254] platform dwc3.0.auto: Added to deferred list > > [ 20.706620] platform dwc3.0.auto: driver_deferred_probe_add_trigger 1 2 > > [ 20.713732] platform dwc3.0.auto: Retrying from deferred list > > [ 20.730035] platform dwc3.0.auto: Driver dwc3 requests probe deferral > > [ 20.736540] platform dwc3.0.auto: Added to deferred list > > [ 20.741889] platform dwc3.0.auto: driver_deferred_probe_add_trigger 3 4 > > [ 20.748991] platform dwc3.0.auto: Retrying from deferred list > > [ 20.765416] platform dwc3.0.auto: Driver dwc3 requests probe deferral > > [ 20.771914] platform dwc3.0.auto: Added to deferred list > > [ 20.777279] platform dwc3.0.auto: driver_deferred_probe_add_trigger 5 6 > > ... > > > > Deeper investigation shows the culprit commit 58b116bce136 > > ("drivercore: deferral race condition fix") which was dedicated to fix some > > other issue while bringing a regression. > > > > This reverts commit 58b116bce13612e5aa6fcd49ecbd4cf8bb59e835 for good until > > we will have better solution. > > > > Cc: Grant Likely > > Cc: Peter Ujfalusi > > Cc: Greg Kroah-Hartman > > Cc: Mark Brown > > Cc: Felipe Balbi > > Cc: Andrzej Hajda > > Signed-off-by: Andy Shevchenko > > --- > > drivers/base/dd.c | 27 ++------------------------- > > 1 file changed, 2 insertions(+), 25 deletions(-) > > Shouldn't there be a "Fixes:" line and cc: stable here? I'm not sure (yet). I would like to hear from people first, especially from Grant (I spoke to him already for the matters at ELCE in Edinburg). Perhaps, Hans can have a chance to test this and comment on. -- With Best Regards, Andy Shevchenko