* Re: [PATCHv2] drivers/perf: arm-ccn: don't log to dmesg in event_init
[not found] <20180521171949.31412-1-mark.rutland@arm.com>
@ 2018-05-21 18:58 ` Kim Phillips
0 siblings, 0 replies; only message in thread
From: Kim Phillips @ 2018-05-21 18:58 UTC (permalink / raw)
To: Mark Rutland
Cc: linux-arm-kernel, will.deacon, Pawel Moll, linux-kernel, perf group
[adding LKML, linux-perf-users. Please do so from now on]
On Mon, 21 May 2018 18:19:49 +0100
Mark Rutland <mark.rutland@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.rutland@arm.com>
> Cc: Pawel Moll <pawel.moll@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> ---
Care to address my comments to the rationale?:
https://marc.info/?l=linux-arm-kernel&m=152582291919277&w=2
Thanks,
Kim
^ permalink raw reply [flat|nested] only message in thread
only message in thread, other threads:[~2018-05-21 18:58 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
[not found] <20180521171949.31412-1-mark.rutland@arm.com>
2018-05-21 18:58 ` [PATCHv2] drivers/perf: arm-ccn: don't log to dmesg in event_init Kim Phillips
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).