Re: [PATCH tracing/kprobes] kprobes: Disable booster when CONFIG_PREEMPT=y

From: Masami Hiramatsu
Date: Fri Jan 29 2010 - 09:50:23 EST

Ingo Molnar wrote:
> * Masami Hiramatsu <mhiramat@xxxxxxxxxx> 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?
>> The booster on preemptive kernel will be resumed if synchronize_tasks() or
>> something like that is introduced.
> such as this one?

Yes, I think this synchronize_tasks(), which just (sleeping) wait until
all currently preempted tasks are wake up and scheduled, can ensure safety.

Thank you,

Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@xxxxxxxxxx

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