Messages in this thread | | | Subject | Re: [PATCH V3 13/18] coresight: tmc: make sysFS and Perf mode mutually exclusive | From | Suzuki K Poulose <> | Date | Mon, 25 Apr 2016 16:11:26 +0100 |
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On 25/04/16 16:05, Mathieu Poirier wrote: > On 25 April 2016 at 08:52, Suzuki K Poulose <Suzuki.Poulose@arm.com> wrote: >> On 25/04/16 15:48, Mathieu Poirier wrote: >>> >>> On 25 April 2016 at 08:32, Suzuki K Poulose <Suzuki.Poulose@arm.com> >>> wrote: >>>> >>>> On 22/04/16 18:14, Mathieu Poirier wrote: >> >> >>>>> + spin_lock_irqsave(&drvdata->spinlock, flags); >>>>> + if (drvdata->reading) { >>>>> + ret = -EINVAL; >>>>> + goto out; >>>>> + } >>>>> + >>>>> + val = local_xchg(&drvdata->mode, mode); >>>>> + /* >>>>> + * In Perf mode there can be only one writer per sink. There >>>>> + * is also no need to continue if the ETR is already operated >>>>> + * from sysFS. >>>>> + */ >>>>> + if (val != CS_MODE_DISABLED) { >>>> >>>> >>>> >>>> Could val be CS_MODE_PERF ? In other words, should we be checking : >>>> if (val == CS_MODE_SYSFS) instead ? >>> >>> >>> If we check for CS_MODE_SYSFS we also have to check for CS_MODE_PERF, >>> which is two checks rather than a single one with the current >>> solution. >> >> >> I am confused now. The comment says, we want to check for sysfs mode and >> don't continue in that case. So, we shouldn't be worried about PERF mode. > > You are correct about the sysFS part, but the first sentence of the > comment also mention that in perf mode there can only be one writer > per sink. Otherwise ring buffers for one session would end up with > traces from other ongoing sessions, and that is not taking into > account the buffer management nightmares it would cause.
OK, in either case, val == CS_MODE_SYSFS is much better check there, to what we want to do
Suzuki
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