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Re: better SMP support for kprobes

From: "Frank Ch. Eigler" <fche at redhat dot com>
To: systemtap at sources dot redhat dot com
Date: Wed, 2 Feb 2005 18:45:26 -0500
Subject: Re: better SMP support for kprobes
References: <1107387079.6053.7.camel@tiger>

Hi -

On Wed, Feb 02, 2005 at 03:31:19PM -0800, Martin Hunt wrote:
> Currently kprobe_handler grabs kprobe_lock and keeps it the entire time
> the probe is executing.  On SMP systems this could cause significant
> performance degradation [...]

More importantly, by reading the code, it seems like kprobes user
functions are called from within a context where interrupts are
blocked.  Would that not make it impossible to safely invoke
user-context might_sleep functions like copy_from_user, from any
of the kprobes, jprobes, dprobes layers?  I hope I'm missing
something!

- FChE

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