From: Arnaldo Carvalho de Melo <acme@infradead.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: linux-kernel@vger.kernel.org, David Ahern <dsahern@gmail.com>,
David Daney <david.daney@cavium.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Jan Beulich <jbeulich@suse.com>,
Joerg Roedel <joerg.roedel@amd.com>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
Mike Galbraith <efault@gmx.de>,
Namhyung Kim <namhyung.kim@lge.com>,
Paul Mackerras <paulus@samba.org>,
Peter Zijlstra <peterz@infradead.org>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Stephane Eranian <eranian@google.com>
Subject: Re: Fixing perf top --user shortcoming was: Re: [GIT PULL 0/9] perf/core improvements and fixes
Date: Thu, 26 Jan 2012 17:24:55 -0200 [thread overview]
Message-ID: <20120126192455.GE9128@infradead.org> (raw)
In-Reply-To: <20120126183223.GB8630@elte.hu>
Em Thu, Jan 26, 2012 at 07:32:23PM +0100, Ingo Molnar escreveu:
>
> * Arnaldo Carvalho de Melo <acme@infradead.org> wrote:
>
> > > > ptrace_may_access(task, PTRACE_MODE_READ) fails for some
> > > > tasks owned by the user because, IIRC, in
> > > > __ptrace_may_access:
> >
> > > Which tasks are these, are they privileged in any sense?
> >
> > IIRC one of them was a child of sshd, that runs as root and
> > then changes the child ownership to the user logging in.
>
> It's probably privileged then - or at least not sufficiently
> deprivileged.
>
> Skipping them ought to be the right solution - it's not like
> such tasks tend to create a lot of overhead worth profiling.
> They are also not debuggable via gdb so they are not part of the
> user's development session and such.
Least convoluted way seems to be just to try to call sys_perf_event_open
on then when building the thread list in thread_new__by_uid(), will try
that after soccer :-)
/me vanishes
- Arnaldo
> > I'll continue investigation but probably for now the first
> > thing to do is to just remove them from the thread_map when
> > they return -EPERM.
>
> Yeah. Maybe warn about them in verbose mode or such.
prev parent reply other threads:[~2012-01-26 19:25 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-24 23:07 [GIT PULL 0/9] perf/core improvements and fixes Arnaldo Carvalho de Melo
2012-01-24 23:07 ` [PATCH 1/9] perf tools: Add fprintf methods for thread_map and cpu_map classes Arnaldo Carvalho de Melo
2012-01-24 23:07 ` [PATCH 2/9] perf tools: Introduce per user view Arnaldo Carvalho de Melo
2012-01-24 23:07 ` [PATCH 3/9] perf bench: Make "default" memcpy() selection actually use glibc's implementation Arnaldo Carvalho de Melo
2012-01-24 23:07 ` [PATCH 4/9] perf bench: Also allow measuring alternative memcpy implementations Arnaldo Carvalho de Melo
2012-01-24 23:07 ` [PATCH 5/9] perf bench: Also allow measuring memset() Arnaldo Carvalho de Melo
2012-01-24 23:07 ` [PATCH 6/9] perf bench: Allow passing an iteration count to "bench mem mem{cpy,set}" Arnaldo Carvalho de Melo
2012-01-24 23:07 ` [PATCH 7/9] perf tools: Fix broken build by defining _GNU_SOURCE in Makefile Arnaldo Carvalho de Melo
2012-01-24 23:08 ` [PATCH 8/9] perf probe: Usability fixes Arnaldo Carvalho de Melo
2012-01-24 23:08 ` [PATCH 9/9] perf tools: Fix strlen() bug in perf_event__synthesize_event_type() Arnaldo Carvalho de Melo
2012-01-26 11:16 ` [GIT PULL 0/9] perf/core improvements and fixes Ingo Molnar
2012-01-26 12:22 ` Fixing perf top --user shortcoming was: " Arnaldo Carvalho de Melo
2012-01-26 13:09 ` Ingo Molnar
2012-01-26 14:30 ` Arnaldo Carvalho de Melo
2012-01-26 18:32 ` Ingo Molnar
2012-01-26 19:24 ` Arnaldo Carvalho de Melo [this message]
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