Messages in this thread | | | Subject | Re: [PATCH v2 21/27] coresight: Convert driver messages to dev_dbg | From | Robert Walker <> | Date | Wed, 2 May 2018 09:25:38 +0100 |
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On 02/05/18 04:55, Kim Phillips wrote: > On Tue, 1 May 2018 10:10:51 +0100 > Suzuki K Poulose <suzuki.poulose@arm.com> wrote: > >> Convert component enable/disable messages from dev_info to dev_dbg. >> This is required to prevent LOCKDEP splats when operating in perf >> mode where we could be called with locks held to enable a coresight > Can we see the splats? Doesn't lockdep turn itself off if it starts > triggering too many splats? > >> path. If someone wants to really see the messages, they can always >> enable it at runtime via dynamic_debug. > Won't the splats still occur when the messages are enabled with > dynamic_debug? > > So in effect this patch only tries to mitigate the splats, all the > while making things harder for regular users that now have to recompile > their kernels, in exchange for a very small convenience for kernel > developers that happen to see a splat or two with DEBUG_LOCKDEP set? > > Not the greatest choice...How about moving the dev_infos outside of the > locks instead? > > Thanks, > > Kim The other reason for making these dev_dbg is performance - a message is output each time a source / link / sink is enabled or disabled, so we can get 20+ messages on each process switch when tracing with perf. This has a significant effect on the runtime of the application being traced.
Regards
Rob
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