On 07/14/2015 08:06 AM, Sakari Ailus wrote: > Hi Shuah, > > Shuah Khan wrote: >> All, >> >> ALSA has to make media_entity_pipeline_start() call in irq >> path. I am seeing warnings that the graph_mutex is unsafe irq >> lock as expected. We have to update MC start/stop pipeline >> to be irq safe for ALSA. Maybe there are other MC interfaces >> that need to be irq safe, but I haven't seen any problems with >> my limited testing. >> >> So as per options, graph_mutex could be changed to a spinlock. >> It looks like drivers hold this lock and it isn't abstracted to >> MC API. Unfortunate, this would require changes to drivers that >> directly hold the lock for graph walks if this mutex is changed >> to spinlock. >> >> e.g: drivers/media/platform/exynos4-is/fimc-isp-video.c >> >> Changes aren't complex, just that the scope isn't limited >> to MC API. >> >> Other ideas?? > > Do you have (preliminary?) patches and / or more information? I'd like > to understand why would ALSA need this. > > The graph_mutex is currently also taken when the link state is modified, > and the callbacks to the drivers may involve power state changes and > device initialisation. On some busses such as I2C these are blocking > operations. > I am getting close to sending the RFC patches for review. I am looking at one last issue in addition to this mutex problem. I have dmesg logs to send and I will send them when I send the patches, so you have code to look at as well as the dmesg. thanks, -- Shuah -- Shuah Khan Sr. Linux Kernel Developer Open Source Innovation Group Samsung Research America (Silicon Valley) shuahkh@xxxxxxxxxxxxxxx | (970) 217-8978 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
