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From: Masami Hiramatsu <mhiramat@kernel.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	Peter Zijlstra <peterz@infradead.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org, bristot@redhat.com,
	jbaron@akamai.com, torvalds@linux-foundation.org,
	tglx@linutronix.de, mingo@kernel.org, namit@vmware.com,
	hpa@zytor.com, luto@kernel.org, ard.biesheuvel@linaro.org,
	jpoimboe@redhat.com, jeyu@kernel.org,
	alexei.starovoitov@gmail.com
Subject: Re: [PATCH -v5 00/17] Rewrite x86/ftrace to use text_poke (and more)
Date: Tue, 26 Nov 2019 17:58:12 +0900	[thread overview]
Message-ID: <20191126175812.c6e0cd1249422989007c91fe@kernel.org> (raw)
In-Reply-To: <20191126091104.5e0cdc61e3b143fae4ed4cfd@kernel.org>

On Tue, 26 Nov 2019 09:11:04 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> On Mon, 25 Nov 2019 12:32:45 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
> 
> > On Mon, 25 Nov 2019 12:55:34 +0900
> > Masami Hiramatsu <mhiramat@kernel.org> wrote:
> > 
> > > void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries)
> > > ...
> > >         on_each_cpu(do_sync_core, NULL, 1);
> > >         /*
> > >          * sync_core() implies an smp_mb() and orders this store against
> > >          * the writing of the new instruction.
> > >          */
> > >         bp_patching.vec = NULL;
> > >         bp_patching.nr_entries = 0;
> > > }
> > > -----
> > > 
> > > I think the "on_each_cpu(do_sync_core, NULL, 1);" can sync the pipeline
> > > but doesn't ensure all ongoing int3 handling is done. Thus, we may need a
> > 
> > How does it not ensure all ongoing int3 handling is done? int3 is done
> > with interrupts disabled, and the on_each_cpu() requires all CPUs to
> > have had their interrupts enabled, thus int3 handling should be
> > completed. Perhaps we need another sync core?
> > 
> > 	on_each_cpu(do_sync_core, NULL, 1);
> > 	bp_patching.nr_entries = 0;
> > 	on_each_cpu(do_sync_core, NULL, 1);
> > 	bp_patching.vec = NULL;
> 
> OK, let me check.
> 
> The 1st sync_core will ensure the poking "int3" is removed. Thus any
> int3-hit address (ip) should NOT match the bp_patching.vec[*].addr after
> that. At this point, "if (likely(!bp_patching.nr_entries))" check does not
> work.
> 
> And the 2nd sync_core will ensure all poke_int3_handler() will see the
> bp_patching.nr_entries = 0.
> After this point, "if (likely(!bp_patching.nr_entries))" works and
> poke_int3_handler() will exit soon. (before touching bp_patching.vec)
> 

Oops, I've tested a bit older kernel (with above change it seems to be fixed).
I'll check the latest -tip.

Thank you,

-- 
Masami Hiramatsu <mhiramat@kernel.org>

  reply	other threads:[~2019-11-26  8:58 UTC|newest]

Thread overview: 106+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-11 13:12 [PATCH -v5 00/17] Rewrite x86/ftrace to use text_poke (and more) Peter Zijlstra
2019-11-11 13:12 ` [PATCH -v5 01/17] x86/alternatives: Teach text_poke_bp() to emulate instructions Peter Zijlstra
2019-11-15  9:43   ` [tip: core/kprobes] " tip-bot2 for Peter Zijlstra
2019-11-11 13:12 ` [PATCH -v5 02/17] x86/alternatives: Update int3_emulate_push() comment Peter Zijlstra
2019-11-15  9:43   ` [tip: core/kprobes] " tip-bot2 for Peter Zijlstra
2019-12-04  8:33   ` tip-bot2 for Peter Zijlstra
2019-11-11 13:12 ` [PATCH -v5 03/17] x86/alternatives,jump_label: Provide better text_poke() batching interface Peter Zijlstra
2019-11-15  9:43   ` [tip: core/kprobes] x86/alternatives, jump_label: " tip-bot2 for Peter Zijlstra
2019-12-04  8:33   ` tip-bot2 for Peter Zijlstra
2019-11-11 13:12 ` [PATCH -v5 04/17] x86/alternatives: Add and use text_gen_insn() helper Peter Zijlstra
2019-11-12 17:10   ` Steven Rostedt
2019-11-12 22:25     ` Peter Zijlstra
2019-11-15  9:43   ` [tip: core/kprobes] " tip-bot2 for Peter Zijlstra
2019-12-04  8:33   ` tip-bot2 for Peter Zijlstra
2019-11-11 13:12 ` [PATCH -v5 05/17] x86/ftrace: Use text_poke() Peter Zijlstra
2019-11-12 18:25   ` Steven Rostedt
2019-11-12 22:24     ` Peter Zijlstra
2019-11-12 22:48       ` Steven Rostedt
2019-11-13  9:01         ` Peter Zijlstra
2019-11-13 14:27           ` Steven Rostedt
2019-11-14 13:18             ` Peter Zijlstra
2019-11-14 13:56               ` Steven Rostedt
2019-11-14 14:05                 ` Peter Zijlstra
2019-11-13  8:53       ` Peter Zijlstra
2019-11-15  9:43   ` [tip: core/kprobes] " tip-bot2 for Peter Zijlstra
2019-11-16 20:46     ` Borislav Petkov
2019-11-18 17:35       ` [PATCH] x86/ftrace: Mark ftrace_modify_code_direct() __ref Borislav Petkov
2019-11-18 17:52         ` Steven Rostedt
2019-11-19  9:55       ` [tip: core/kprobes] " tip-bot2 for Borislav Petkov
2019-12-04  8:33       ` tip-bot2 for Borislav Petkov
2019-12-04  8:33   ` [tip: core/kprobes] x86/ftrace: Use text_poke() tip-bot2 for Peter Zijlstra
2019-11-11 13:12 ` [PATCH -v5 06/17] x86/mm: Remove set_kernel_text_r[ow]() Peter Zijlstra
2019-11-15  9:43   ` [tip: core/kprobes] " tip-bot2 for Peter Zijlstra
2019-12-04  8:33   ` tip-bot2 for Peter Zijlstra
2019-11-11 13:12 ` [PATCH -v5 07/17] x86/alternative: Add text_opcode_size() Peter Zijlstra
2019-11-15  9:43   ` [tip: core/kprobes] " tip-bot2 for Peter Zijlstra
2019-12-04  8:33   ` tip-bot2 for Peter Zijlstra
2019-11-11 13:13 ` [PATCH -v5 08/17] x86/ftrace: Use text_gen_insn() Peter Zijlstra
2019-11-15  9:43   ` [tip: core/kprobes] " tip-bot2 for Peter Zijlstra
2019-12-04  8:33   ` tip-bot2 for Peter Zijlstra
2019-11-11 13:13 ` [PATCH -v5 09/17] x86/alternative: Remove text_poke_loc::len Peter Zijlstra
2019-11-15  9:43   ` [tip: core/kprobes] " tip-bot2 for Peter Zijlstra
2019-12-04  8:33   ` tip-bot2 for Peter Zijlstra
2019-11-11 13:13 ` [PATCH -v5 10/17] x86/alternative: Shrink text_poke_loc Peter Zijlstra
2019-11-15  9:43   ` [tip: core/kprobes] " tip-bot2 for Peter Zijlstra
2019-12-04  8:33   ` tip-bot2 for Peter Zijlstra
2019-11-11 13:13 ` [PATCH -v5 11/17] x86/kprobes: Convert to text-patching.h Peter Zijlstra
2019-11-19 16:56   ` [tip: core/kprobes] " tip-bot2 for Peter Zijlstra
2019-12-04  8:33   ` tip-bot2 for Peter Zijlstra
2019-11-11 13:13 ` [PATCH -v5 12/17] x86/kprobes: Fix ordering Peter Zijlstra
2019-11-13 14:31   ` Paul E. McKenney
2019-11-13 15:42   ` Mathieu Desnoyers
2019-11-14 13:53     ` Peter Zijlstra
2019-11-14 15:06       ` Mathieu Desnoyers
2019-11-14 15:13         ` Paul E. McKenney
2019-11-14 15:22           ` Mathieu Desnoyers
2019-11-14 15:28             ` Peter Zijlstra
2019-11-14 15:30               ` Mathieu Desnoyers
2019-11-14 15:42                 ` Peter Zijlstra
2019-11-14 15:58                   ` Peter Zijlstra
2019-11-19 16:56   ` [tip: core/kprobes] x86/kprobes: Fix ordering while text-patching tip-bot2 for Peter Zijlstra
2019-12-04  8:33   ` tip-bot2 for Peter Zijlstra
2019-11-11 13:13 ` [PATCH -v5 13/17] arm/ftrace: Use __patch_text_real() Peter Zijlstra
2019-11-11 16:47   ` Will Deacon
2019-11-11 17:19     ` Peter Zijlstra
2019-11-11 17:25       ` Peter Zijlstra
2019-11-12 11:29         ` Will Deacon
2019-11-13  9:26           ` [PATCH -v5mkII 13/17] arm/ftrace: Use __patch_text() Peter Zijlstra
2019-11-19 16:56             ` [tip: core/kprobes] " tip-bot2 for Peter Zijlstra
2019-12-04  8:33             ` tip-bot2 for Peter Zijlstra
2020-01-22 21:26               ` Dmitry Osipenko
2020-02-07 10:17                 ` Peter Zijlstra
2020-02-07 10:26                   ` Peter Zijlstra
2020-02-07 11:27                 ` Peter Zijlstra
2020-02-07 16:47                   ` Dmitry Osipenko
2020-01-08 12:22             ` [PATCH -v5mkII 13/17] " Arnd Bergmann
2020-01-08 14:16               ` Steven Rostedt
2020-01-08 14:22                 ` Arnd Bergmann
2019-11-11 13:13 ` [PATCH -v5 14/17] module: Remove set_all_modules_text_*() Peter Zijlstra
2019-11-19 16:56   ` [tip: core/kprobes] " tip-bot2 for Peter Zijlstra
2019-12-04  8:33   ` tip-bot2 for Peter Zijlstra
2019-11-11 13:13 ` [PATCH -v5 15/17] ftrace: Rework event_create_dir() Peter Zijlstra
2019-11-14 14:07   ` Steven Rostedt
2019-11-19 16:56   ` [tip: core/kprobes] " tip-bot2 for Peter Zijlstra
2019-12-04  8:33   ` tip-bot2 for Peter Zijlstra
2019-11-11 13:13 ` [PATCH -v5 16/17] x86/kprobe: Add comments to arch_{,un}optimize_kprobes() Peter Zijlstra
2019-11-19 16:56   ` [tip: core/kprobes] " tip-bot2 for Peter Zijlstra
2019-12-04  8:33   ` tip-bot2 for Peter Zijlstra
2019-11-11 13:13 ` [PATCH -v5 17/17] x86/alternative: Use INT3_INSN_SIZE Peter Zijlstra
2019-11-19 16:56   ` [tip: core/kprobes] x86/alternatives: " tip-bot2 for Peter Zijlstra
2019-12-04  8:33   ` tip-bot2 for Peter Zijlstra
2019-11-11 19:47 ` [PATCH -v5 00/17] Rewrite x86/ftrace to use text_poke (and more) Alexei Starovoitov
2019-11-11 20:39   ` Peter Zijlstra
2019-11-11 20:42   ` Peter Zijlstra
2019-11-11 20:56     ` Alexei Starovoitov
2019-11-12 18:26 ` Steven Rostedt
2019-11-25  3:55 ` Masami Hiramatsu
2019-11-25  6:47   ` Masami Hiramatsu
2019-11-25 17:32   ` Steven Rostedt
2019-11-26  0:11     ` Masami Hiramatsu
2019-11-26  8:58       ` Masami Hiramatsu [this message]
2019-11-26  9:58         ` Masami Hiramatsu
2019-11-26 23:48           ` Masami Hiramatsu
     [not found]             ` <CAADnVQK4twuXzFhD-qLHmCVK0n1h-GDENQLu+4PVV3Hp++R6kQ@mail.gmail.com>
2019-11-27  4:32               ` Alexei Starovoitov
2019-11-27  5:01                 ` Alexei Starovoitov
2019-11-27  6:41                 ` Masami Hiramatsu

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