From: Ingo Molnar <mingo@elte.hu>
To: Jan Beulich <JBeulich@novell.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Thomas Gleixner <tglx@linutronix.de>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH 5/6] x86: Remove useless unwinder backlink from irq regs saving
Date: Mon, 4 Jul 2011 11:17:42 +0200 [thread overview]
Message-ID: <20110704091742.GC22943@elte.hu> (raw)
In-Reply-To: <4E1187E4020000780004BF2C@nat28.tlf.novell.com>
* Jan Beulich <JBeulich@novell.com> wrote:
> >>> On 02.07.11 at 18:29, Frederic Weisbecker <fweisbec@gmail.com> wrote:
> > The unwinder backlink in interrupt entry is very useless.
> > It's actually not part of the stack frame chain and thus is
> > never used.
>
> I very much doubt this - see dump_trace()'s comment in its IRQ-stack
> related code portion (and the corresponding use of irq_stack_end[-1]).
> > +++ b/arch/x86/kernel/entry_64.S
> > @@ -327,7 +327,6 @@ ENDPROC(native_usergs_sysret64)
> > jne 2f
> > mov PER_CPU_VAR(irq_stack_ptr),%rsp
> > EMPTY_FRAME 0
> > - pushq_cfi %rbp /* backlink for unwinder */
> > /*
> > * We entered an interrupt context - irqs are off:
> > */
Frederic, please add it back with a much better comment in the .S
showing where it's used and how. Perhaps even try to trigger the
usage of this backlink and document the effect in the changelog.
Thanks,
Ingo
next prev parent reply other threads:[~2011-07-04 9:17 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-02 16:29 [RFC GIT PULL] x86 entry / perf stacktrace changes Frederic Weisbecker
2011-07-02 16:29 ` [PATCH 1/6] x86: Save stack pointer in perf live regs savings Frederic Weisbecker
2011-07-02 16:29 ` [PATCH 2/6] x86: Fetch stack from regs when possible in dump_trace() Frederic Weisbecker
2011-07-02 16:29 ` [PATCH 3/6] x86,64: Simplify save_regs() Frederic Weisbecker
2011-07-04 7:20 ` Jan Beulich
2011-07-04 12:57 ` Frederic Weisbecker
2011-07-06 17:34 ` Andi Kleen
2011-07-06 18:20 ` H. Peter Anvin
2011-07-06 20:42 ` Frederic Weisbecker
2011-07-04 12:59 ` Frederic Weisbecker
2011-07-02 16:29 ` [PATCH 4/6] x86,64: Separate arg1 from rbp handling in SAVE_REGS_IRQ Frederic Weisbecker
2011-07-04 7:34 ` Jan Beulich
2011-07-02 16:29 ` [PATCH 5/6] x86: Remove useless unwinder backlink from irq regs saving Frederic Weisbecker
2011-07-04 7:29 ` Jan Beulich
2011-07-04 9:17 ` Ingo Molnar [this message]
2011-07-04 13:10 ` Frederic Weisbecker
2011-07-04 13:22 ` Frederic Weisbecker
2011-07-05 22:21 ` Valdis.Kletnieks
2011-07-02 16:29 ` [PATCH 6/6] x86: Don't use frame pointer to save old stack on irq entry Frederic Weisbecker
2011-07-04 9:13 ` [RFC GIT PULL] x86 entry / perf stacktrace changes Ingo Molnar
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