lkml.org 
[lkml]   [2017]   [Sep]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] arm64: Unconditionally support ARCH_HAVE_NMI_SAFE_CMPXCHG
On 09/15, James Morse wrote:
> On 15/09/17 02:19, Stephen Boyd wrote:
> > From what I can see there isn't anything about ACPI_APEI_SEA that
> > means the arm64 architecture can or cannot support NMI safe
> > cmpxchg, so the if condition here is not important.
>
> Yup, it was to match 'HAVE_NMI', which was new with ACPI_APEI_SEA and pulls in
> some printk() stuff.
>
> ... how come you don't need to change HAVE_NMI too?

I didn't change HAVE_NMI because it wasn't needed to get hist
triggers working. Sorry, I didn't even notice that HAVE_NMI
was also there, probably both of these configs should drop the
condition. I'll update the patch to do so.

>
>
> > Let's remove
> > it. Doing that allows us to support ftrace histograms via
> > CONFIG_HIST_TRIGGERS that depends on the arch having this config
> > selected.
>
> What does CONFIG_HIST_TRIGGERS need this for? I can't see any
> cmpxchg use in kernel/trace/trace_events_hist.c

True. I think this isn't necessary for CONFIG_HIST_TRIGGERS, but
more for CONFIG_TRACING_MAP that is selected and used by
CONFIG_HIST_TRIGGERS. We put the dependency in both places so we
don't get the trigger config selecting a config that has unmet
dependencies. Note there's a cmpxchg in the tracing map code too.

--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

\
 
 \ /
  Last update: 2017-09-15 21:16    [W:0.039 / U:0.160 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site