From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 377C2C433FE for ; Tue, 26 Oct 2021 12:01:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 207BD60F0F for ; Tue, 26 Oct 2021 12:01:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235126AbhJZMDq convert rfc822-to-8bit (ORCPT ); Tue, 26 Oct 2021 08:03:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:34966 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229786AbhJZMDp (ORCPT ); Tue, 26 Oct 2021 08:03:45 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 425F3601FC; Tue, 26 Oct 2021 12:01:19 +0000 (UTC) Date: Tue, 26 Oct 2021 08:01:17 -0400 From: Steven Rostedt To: =?UTF-8?B?546L6LSH?= Cc: Miroslav Benes , Guo Ren , Ingo Molnar , "James E.J. Bottomley" , Helge Deller , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Paul Walmsley , Palmer Dabbelt , Albert Ou , Thomas Gleixner , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Josh Poimboeuf , Jiri Kosina , Petr Mladek , Joe Lawrence , Masami Hiramatsu , "Peter Zijlstra (Intel)" , Nicholas Piggin , Jisheng Zhang , linux-csky@vger.kernel.org, linux-kernel@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, live-patching@vger.kernel.org Subject: Re: [PATCH v5 1/2] ftrace: disable preemption when recursion locked Message-ID: <20211026080117.366137a5@gandalf.local.home> In-Reply-To: <18ba2a71-e12d-33f7-63fe-2857b2db022c@linux.alibaba.com> References: <3ca92dc9-ea04-ddc2-71cd-524bfa5a5721@linux.alibaba.com> <333cecfe-3045-8e0a-0c08-64ff590845ab@linux.alibaba.com> <18ba2a71-e12d-33f7-63fe-2857b2db022c@linux.alibaba.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On Tue, 26 Oct 2021 17:48:10 +0800 王贇 wrote: > > The two comments should be updated too since Steven removed the "bit == 0" > > trick. > > Could you please give more hint on how will it be correct? > > I get the point that bit will no longer be 0, there are only -1 or > 0 now > so trace_test_and_set_recursion() will disable preemption on bit > 0 and > trace_clear_recursion() will enabled it since it should only be called when > bit > 0 (I remember we could use a WARN_ON here now :-P). > > > > >> @@ -178,7 +187,7 @@ static __always_inline void trace_clear_recursion(int bit) > >> * tracing recursed in the same context (normal vs interrupt), > >> * > >> * Returns: -1 if a recursion happened. > >> - * >= 0 if no recursion > >> + * > 0 if no recursion. > >> */ > >> static __always_inline int ftrace_test_recursion_trylock(unsigned long ip, > >> unsigned long parent_ip) > > > > And this change would not be correct now. > > I thought it will no longer return 0 so I change it to > 0, isn't that correct? No it is not. I removed the bit + 1 return value, which means it returns the actual bit now. Which is 0 or more. -- Steve From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 222E6C433EF for ; Tue, 26 Oct 2021 12:01:35 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C040A60F0F for ; Tue, 26 Oct 2021 12:01:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org C040A60F0F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=aVrtfU3CsDcZX9/x7d4fFwC2yZMjRGqdyQZMP4ik9ZI=; b=XbCY0zaOPc6P2d VC57X1khknF6JjJZOz7NnqdDMoLj2P4FPvTCvcODLJnlxWdCjWc8Wp5Phg9oFZsZx48xPXwbjXUrf DloctPLuMauHCojFfNJV5n0c/glyb4ers8QWzxPlmxIxClkItMMxSwNdp6r4lzu1b/Ae+2VKJipMq 75794YW19Z1AK5ZxRv3R1pP/nyasdFrYMp6ovk5Xa+YEenT0/A7z2Ws1YX4duZhulmjLM9F3iN54M Vrke9LZLGIGNghvUqo9hA8VkRrL9Izj9/ntH3cImGYSWCHsC57XsLY71cHs/Csp0gUygNfPh3qBoW l9SdceU+t5KrnVPQX+wA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mfL8u-001ivf-Mo; Tue, 26 Oct 2021 12:01:24 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mfL8s-001iuU-2f for linux-riscv@lists.infradead.org; Tue, 26 Oct 2021 12:01:23 +0000 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 425F3601FC; Tue, 26 Oct 2021 12:01:19 +0000 (UTC) Date: Tue, 26 Oct 2021 08:01:17 -0400 From: Steven Rostedt To: =?UTF-8?B?546L6LSH?= Cc: Miroslav Benes , Guo Ren , Ingo Molnar , "James E.J. Bottomley" , Helge Deller , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Paul Walmsley , Palmer Dabbelt , Albert Ou , Thomas Gleixner , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Josh Poimboeuf , Jiri Kosina , Petr Mladek , Joe Lawrence , Masami Hiramatsu , "Peter Zijlstra (Intel)" , Nicholas Piggin , Jisheng Zhang , linux-csky@vger.kernel.org, linux-kernel@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, live-patching@vger.kernel.org Subject: Re: [PATCH v5 1/2] ftrace: disable preemption when recursion locked Message-ID: <20211026080117.366137a5@gandalf.local.home> In-Reply-To: <18ba2a71-e12d-33f7-63fe-2857b2db022c@linux.alibaba.com> References: <3ca92dc9-ea04-ddc2-71cd-524bfa5a5721@linux.alibaba.com> <333cecfe-3045-8e0a-0c08-64ff590845ab@linux.alibaba.com> <18ba2a71-e12d-33f7-63fe-2857b2db022c@linux.alibaba.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211026_050122_167537_1FE11B22 X-CRM114-Status: GOOD ( 21.58 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org T24gVHVlLCAyNiBPY3QgMjAyMSAxNzo0ODoxMCArMDgwMArnjovotIcgPHl1bi53YW5nQGxpbnV4 LmFsaWJhYmEuY29tPiB3cm90ZToKCj4gPiBUaGUgdHdvIGNvbW1lbnRzIHNob3VsZCBiZSB1cGRh dGVkIHRvbyBzaW5jZSBTdGV2ZW4gcmVtb3ZlZCB0aGUgImJpdCA9PSAwIiAKPiA+IHRyaWNrLiAg Cj4gCj4gQ291bGQgeW91IHBsZWFzZSBnaXZlIG1vcmUgaGludCBvbiBob3cgd2lsbCBpdCBiZSBj b3JyZWN0Pwo+IAo+IEkgZ2V0IHRoZSBwb2ludCB0aGF0IGJpdCB3aWxsIG5vIGxvbmdlciBiZSAw LCB0aGVyZSBhcmUgb25seSAtMSBvciA+IDAgbm93Cj4gc28gdHJhY2VfdGVzdF9hbmRfc2V0X3Jl Y3Vyc2lvbigpIHdpbGwgZGlzYWJsZSBwcmVlbXB0aW9uIG9uIGJpdCA+IDAgYW5kCj4gdHJhY2Vf Y2xlYXJfcmVjdXJzaW9uKCkgd2lsbCBlbmFibGVkIGl0IHNpbmNlIGl0IHNob3VsZCBvbmx5IGJl IGNhbGxlZCB3aGVuCj4gYml0ID4gMCAoSSByZW1lbWJlciB3ZSBjb3VsZCB1c2UgYSBXQVJOX09O IGhlcmUgbm93IDotUCkuCj4gCj4gPiAgIAo+ID4+IEBAIC0xNzgsNyArMTg3LDcgQEAgc3RhdGlj IF9fYWx3YXlzX2lubGluZSB2b2lkIHRyYWNlX2NsZWFyX3JlY3Vyc2lvbihpbnQgYml0KQo+ID4+ ICAgKiB0cmFjaW5nIHJlY3Vyc2VkIGluIHRoZSBzYW1lIGNvbnRleHQgKG5vcm1hbCB2cyBpbnRl cnJ1cHQpLAo+ID4+ICAgKgo+ID4+ICAgKiBSZXR1cm5zOiAtMSBpZiBhIHJlY3Vyc2lvbiBoYXBw ZW5lZC4KPiA+PiAtICogICAgICAgICAgID49IDAgaWYgbm8gcmVjdXJzaW9uCj4gPj4gKyAqICAg ICAgICAgICA+IDAgaWYgbm8gcmVjdXJzaW9uLgo+ID4+ICAgKi8KPiA+PiAgc3RhdGljIF9fYWx3 YXlzX2lubGluZSBpbnQgZnRyYWNlX3Rlc3RfcmVjdXJzaW9uX3RyeWxvY2sodW5zaWduZWQgbG9u ZyBpcCwKPiA+PiAgCQkJCQkJCSB1bnNpZ25lZCBsb25nIHBhcmVudF9pcCkgIAo+ID4gCj4gPiBB bmQgdGhpcyBjaGFuZ2Ugd291bGQgbm90IGJlIGNvcnJlY3Qgbm93LiAgCj4gCj4gSSB0aG91Z2h0 IGl0IHdpbGwgbm8gbG9uZ2VyIHJldHVybiAwIHNvIEkgY2hhbmdlIGl0IHRvID4gMCwgaXNuJ3Qg dGhhdCBjb3JyZWN0PwoKTm8gaXQgaXMgbm90LiBJIHJlbW92ZWQgdGhlIGJpdCArIDEgcmV0dXJu IHZhbHVlLCB3aGljaCBtZWFucyBpdCByZXR1cm5zIHRoZQphY3R1YWwgYml0IG5vdy4gV2hpY2gg aXMgMCBvciBtb3JlLgoKLS0gU3RldmUKCl9fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fCmxpbnV4LXJpc2N2IG1haWxpbmcgbGlzdApsaW51eC1yaXNjdkBsaXN0 cy5pbmZyYWRlYWQub3JnCmh0dHA6Ly9saXN0cy5pbmZyYWRlYWQub3JnL21haWxtYW4vbGlzdGlu Zm8vbGludXgtcmlzY3YK From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 90413C433F5 for ; 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Tue, 26 Oct 2021 23:01:24 +1100 (AEDT) Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 425F3601FC; Tue, 26 Oct 2021 12:01:19 +0000 (UTC) Date: Tue, 26 Oct 2021 08:01:17 -0400 From: Steven Rostedt To: =?UTF-8?B?546L6LSH?= Subject: Re: [PATCH v5 1/2] ftrace: disable preemption when recursion locked Message-ID: <20211026080117.366137a5@gandalf.local.home> In-Reply-To: <18ba2a71-e12d-33f7-63fe-2857b2db022c@linux.alibaba.com> References: <3ca92dc9-ea04-ddc2-71cd-524bfa5a5721@linux.alibaba.com> <333cecfe-3045-8e0a-0c08-64ff590845ab@linux.alibaba.com> <18ba2a71-e12d-33f7-63fe-2857b2db022c@linux.alibaba.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Peter Zijlstra \(Intel\)" , Paul Walmsley , "James E.J. Bottomley" , Guo Ren , Jisheng Zhang , "H. Peter Anvin" , live-patching@vger.kernel.org, linux-riscv@lists.infradead.org, Miroslav Benes , Joe Lawrence , Helge Deller , x86@kernel.org, linux-csky@vger.kernel.org, Ingo Molnar , Petr Mladek , Albert Ou , Jiri Kosina , Nicholas Piggin , Borislav Petkov , Josh Poimboeuf , Thomas Gleixner , linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org, Palmer Dabbelt , Masami Hiramatsu , Paul Mackerras , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, 26 Oct 2021 17:48:10 +0800 =E7=8E=8B=E8=B4=87 wrote: > > The two comments should be updated too since Steven removed the "bit = =3D=3D 0"=20 > > trick. =20 >=20 > Could you please give more hint on how will it be correct? >=20 > I get the point that bit will no longer be 0, there are only -1 or > 0 now > so trace_test_and_set_recursion() will disable preemption on bit > 0 and > trace_clear_recursion() will enabled it since it should only be called wh= en > bit > 0 (I remember we could use a WARN_ON here now :-P). >=20 > > =20 > >> @@ -178,7 +187,7 @@ static __always_inline void trace_clear_recursion(= int bit) > >> * tracing recursed in the same context (normal vs interrupt), > >> * > >> * Returns: -1 if a recursion happened. > >> - * >=3D 0 if no recursion > >> + * > 0 if no recursion. > >> */ > >> static __always_inline int ftrace_test_recursion_trylock(unsigned lon= g ip, > >> unsigned long parent_ip) =20 > >=20 > > And this change would not be correct now. =20 >=20 > I thought it will no longer return 0 so I change it to > 0, isn't that co= rrect? No it is not. I removed the bit + 1 return value, which means it returns the actual bit now. Which is 0 or more. -- Steve