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Re: [PATCH tracing/kprobes] kprobes: Disable booster when CONFIG_PREEMPT=y
- From: Peter Zijlstra <peterz at infradead dot org>
- To: Ingo Molnar <mingo at elte dot hu>
- Cc: Masami Hiramatsu <mhiramat at redhat dot com>, Thomas Gleixner <tglx at linutronix dot de>, Fr??d??ric Weisbecker <fweisbec at gmail dot com>, Steven Rostedt <rostedt at goodmis dot org>, lkml <linux-kernel at vger dot kernel dot org>, systemtap <systemtap at sources dot redhat dot com>, DLE <dle-develop at lists dot sourceforge dot net>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Jim Keniston <jkenisto at us dot ibm dot com>, Mathieu Desnoyers <compudj at krystal dot dyndns dot org>
- Date: Fri, 29 Jan 2010 12:30:48 +0100
- Subject: Re: [PATCH tracing/kprobes] kprobes: Disable booster when CONFIG_PREEMPT=y
- References: <4B5E476C.9030303@redhat.com> <20100127215531.24775.26807.stgit@dhcp-100-2-132.bos.redhat.com> <20100129092135.GE10878@elte.hu>
On Fri, 2010-01-29 at 10:21 +0100, Ingo Molnar wrote:
> * Masami Hiramatsu <mhiramat@redhat.com> wrote:
>
> > Disable kprobe booster when CONFIG_PREEMPT=y, because it can't ensure that
> > all kernel threads preempted on kprobe's boosted slot run out from the slot
> > even using freeze_processes().
>
> hm, this really sucks as it makes preemptible kernels perform worse. Is there
> no better solution?
We could pre-allocate 1 slot per kernel thread.