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From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	namhyung@kernel.org, Ingo Molnar <mingo@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH perf/core ] perf-probe: Check kprobes blacklist when adding new events
Date: Wed, 25 Feb 2015 18:50:05 -0300
Message-ID: <20150225215005.GL18705@kernel.org> (raw)
In-Reply-To: <20150219143113.14434.5387.stgit@localhost.localdomain>

Em Thu, Feb 19, 2015 at 11:31:13PM +0900, Masami Hiramatsu escreveu:
> Recent linux kernel provides a blacklist of the functions which
> can not be probed. perf probe can now check this blacklist before
> setting new events and indicate better error message for users.
> 
> Without this patch,
>   ----
>   # perf probe --add vmalloc_fault
>   Added new event:
>   Failed to write event: Invalid argument
>     Error: Failed to add events.
>   ----
> With this patch
>   ----
>   # perf probe --add vmalloc_fault
>   Added new event:
>   Warning: Skipped probing on blacklisted function: vmalloc_fault
>   ----
> 
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> Reported-by: Arnaldo Carvalho de Melo <acme@kernel.org>

Ok, I really need to use a newer kernel on this RHEL7 box, a 4.0-rc one,
as when trying this I saw no difference, but probably that is because it
didn't find the kprobes blacklist, tried inserting the probe and then
failed with the exact previous message...

A follow up patch could try to improve the situation by saying something
like:

"Failed to insert the probe, maybe this is a blacklisted function and
you're running an old kernel?

Please check the function definition, it should not be marked as, for
instance:

  NOKPROBE_SYMBOL(vmalloc_fault);"

Anyway, applying your patch, clearly an improvement when the blacklist
is available.

Thanks,

- Arnaldo

  reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-30  9:37 [PATCH perf/core 0/2] perf-probe: bugfix and update Masami Hiramatsu
2015-01-30  9:37 ` [PATCH perf/core 1/2] [BUGFIX] perf-probe: Fix to handle optimized not-inlined but has no instance Masami Hiramatsu
2015-01-30 14:21   ` Arnaldo Carvalho de Melo
2015-01-30 14:32     ` Arnaldo Carvalho de Melo
2015-02-02  8:41       ` Masami Hiramatsu
2015-02-08  8:37     ` Masami Hiramatsu
2015-02-11 20:42       ` Arnaldo Carvalho de Melo
2015-02-19 14:31         ` [PATCH perf/core ] perf-probe: Check kprobes blacklist when adding new events Masami Hiramatsu
2015-02-25 21:50           ` Arnaldo Carvalho de Melo [this message]
2015-02-28  9:30           ` [tip:perf/core] perf probe: " tip-bot for Masami Hiramatsu
2015-02-18 18:25   ` [tip:perf/core] perf probe: Fix to handle optimized not-inlined functions tip-bot for Masami Hiramatsu
2015-01-30  9:37 ` [PATCH perf/core 2/2] [DOC] perf-probe: Update perf-probe document Masami Hiramatsu
2015-02-18 18:25   ` [tip:perf/core] perf probe: Update man page tip-bot for Masami Hiramatsu

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