Hi Greg, Grant, On 04/09/2014 01:52 PM, Peter Ujfalusi wrote: > Hi, > > Changes since v1: > - The deferral race detection and handling has been moved to > driver_deferred_probe_trigger() and driver_deferred_probe_add() functions > with > comment section. > - driver_deferred_probe_add/del function needed to be moved. Both of them > placed > after driver_deferred_probe_trigger() so they remain together. > - I have not added the Acked-by from Mark and Grant since the patch itself > changed from v1, but the functionality remained.
Is this solution sounds good? Do you want me to resend the two patch? Regards, Péter > Explanantion of the issue (from patch 2): > When the kernel is built with CONFIG_PREEMPT it is possible to reach a state > when all modules loaded but some driver still stuck in the deferred list > and there is a need for external event to kick the deferred queue to probe > these drivers. > > The issue has been observed on embedded systems with CONFIG_PREEMPT enabled, > audio support built as modules and using nfsroot for root filesystem. > > The following log fragment shows such sequence when all audio modules > were loaded but the sound card is not present since the machine driver has > failed to probe due to missing dependency during it's probe. > The board is am335x-evmsk (McASP<->tlv320aic3106 codec) with davinci-evm > machine driver: > > ... > [ 12.615118] davinci-mcasp 4803c000.mcasp: davinci_mcasp_probe: ENTER > [ 12.719969] davinci_evm sound.3: davinci_evm_probe: ENTER > [ 12.725753] davinci_evm sound.3: davinci_evm_probe: snd_soc_register_card > [ 12.753846] davinci-mcasp 4803c000.mcasp: davinci_mcasp_probe: > snd_soc_register_component > [ 12.922051] davinci-mcasp 4803c000.mcasp: davinci_mcasp_probe: > snd_soc_register_component DONE > [ 12.950839] davinci_evm sound.3: ASoC: platform (null) not registered > [ 12.957898] davinci_evm sound.3: davinci_evm_probe: snd_soc_register_card > DONE (-517) > [ 13.099026] davinci-mcasp 4803c000.mcasp: Kicking the deferred list > [ 13.177838] davinci-mcasp 4803c000.mcasp: really_probe: probe_count = 2 > [ 13.194130] davinci_evm sound.3: snd_soc_register_card failed (-517) > [ 13.346755] davinci_mcasp_driver_init: LEAVE > [ 13.377446] platform sound.3: Driver davinci_evm requests probe deferral > [ 13.592527] platform sound.3: really_probe: probe_count = 0 > > In the log the machine driver enters it's probe at 12.719969 (this point it > has been removed from the deferred lists). McASP driver already executing > it's probing (since 12.615118). > The machine driver tries to construct the sound card (12.950839) but did > not found one of the components so it fails. After this McASP driver > registers all the ASoC components (the machine driver still in it's probe > function after it failed to construct the card) and the deferred work is > prepared at 13.099026 (note that this time the machine driver is not in the > lists so it is not going to be handled when the work is executing). > Lastly the machine driver exit from it's probe and the core places it to > the deferred list but there will be no other driver going to load and the > deferred queue is not going to be kicked again - till we have external event > like connecting USB stick, etc. > > The proposed solution is to try the deferred queue once more when the last > driver is asking for deferring and we had drivers loaded while this last > driver was probing. > > This way we can avoid drivers stuck in the deferred queue. > > Regards, > Peter > --- > Peter Ujfalusi (2): > drivercore: dd: Move driver_deferred_probe_add/del function down in > the code > drivercore: deferral race condition fix > > drivers/base/dd.c | 71 > +++++++++++++++++++++++++++++++++++++------------------ > 1 file changed, 48 insertions(+), 23 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
