[adding LKML, linux-perf-users. Please do so from now on] On Mon, 21 May 2018 18:19:49 +0100 Mark Rutland <mark.rutl...@arm.com> wrote:
> The ARM CCN PMU driver uses dev_warn() to complain about parameters in > the user-provided perf_event_attr. This means that under normal > operation (e.g. a single invocation of the perf tool), a number of > messages warnings may be logged to dmesg. > > Tools may issue multiple syscalls to probe for feature support, and > multiple applications (from multiple users) can attempt to open events > simultaneously, so this is not very helpful, even if a user happens to > have access to dmesg. Worse, this can push important information out of > the dmesg ring buffer, and can significantly slow down syscall fuzzers, > vastly increasing the time it takes to find critical bugs. > > Demote the dev_warn() instances to dev_dbg(), as is the case for all > other PMU drivers under drivers/perf/. Users who wish to debug PMU event > initialisation can enable dynamic debug to receive these messages. > > Signed-off-by: Mark Rutland <mark.rutl...@arm.com> > Cc: Pawel Moll <pawel.m...@arm.com> > Cc: Will Deacon <will.dea...@arm.com> > --- Care to address my comments to the rationale?: https://marc.info/?l=linux-arm-kernel&m=152582291919277&w=2 Thanks, Kim
