linux-kernel - Re: [Bug 10489] Kprobe smoke test lockdep warning

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Message-ID: <480D1B14.7070806@redhat.com>
Date:	Mon, 21 Apr 2008 18:54:12 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Adrian Bunk <bunk@...nel.org>
CC:	ananth@...ibm.com, anil.s.keshavamurthy@...el.com,
	davem@...emloft.net, bugme-daemon@...zilla.kernel.org,
	jean-marc LACROIX <jeanmarc.lacroix@...e.Fr>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [Bug 10489] Kprobe smoke test lockdep warning

Thank you for reporting.

Actually, kprobes tries to fixup thread's flags in post_kprobe_handler
(which is called from kprobe_exceptions_notify) by
trace_hardirqs_fixup_flags(pt_regs->flags). However, even the irq flag
is set in pt_regs->flags, true hardirq is still off until returning
from do_debug. Thus, lockdep assumes that hardirq is off without annotation.

IMHO, one possible solution is that fixing hardirq flags right after
notify_die in do_debug instead of in post_kprobe_handler.

Thanks,

-- 
Masami Hiramatsu

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

e-mail: mhiramat@...hat.com

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