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 B2DB6C4332F for ; Tue, 19 Oct 2021 13:26:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9EA766137C for ; Tue, 19 Oct 2021 13:26:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235828AbhJSN2k (ORCPT ); Tue, 19 Oct 2021 09:28:40 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:59936 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235754AbhJSN2i (ORCPT ); Tue, 19 Oct 2021 09:28:38 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1634649985; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=bUbADiikNrKItOeyvl1XlM9vGXDNaqE+WJmF5wYrcJI=; b=CYuXVRkmsVbk9lVVonDcwaJdK1mpvpjCwXNytbPFKqBtZWbQj6FJEPXJT3NcIyqTfD0pbZ XXhDvzdnEAZIhkdGs5ms6KSekX4SKUyGI2TxTsba3HVZ6pCuo8TgYUD2F1wibtTpnOMXtn aTW4/TK/7dOXhzWGA2SyDxotWhkraIs= Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-410-xsvtD3TmMFWVuXj4sndsTA-1; Tue, 19 Oct 2021 09:26:24 -0400 X-MC-Unique: xsvtD3TmMFWVuXj4sndsTA-1 Received: by mail-ed1-f69.google.com with SMTP id d3-20020a056402516300b003db863a248eso17557151ede.16 for ; Tue, 19 Oct 2021 06:26:24 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=bUbADiikNrKItOeyvl1XlM9vGXDNaqE+WJmF5wYrcJI=; b=huFWptDX1YOjrFJqaLCOsZ7TXXuArXOML5AhB+AJ12ApuqN1UVfDRpBSX0x4DhqyAe rxq7xVFzx1agYyE9DskOdYA0nwRtQe+mLf1m0czshZMoGzxrlcEPyjr3NAXx86nQjma+ g7gProuyy46qEe1DcFWoU+1dsAJCvGo1pWRydU13D+11jE/6AejKylMcesWTVQnsUkmf RNFor9QVy0FfdVZ7P2jkxJlbYDPtY2SuqbERf7S5u7VPpfNANONTMkkHvNxHjnUjp9WY XNtkcEyiMQbBfsNH2kyDlHz9GJzYkBHfjb2TsFm5srq/X/iGrt38ayQRVkEnZsX9JHlD JRCA== X-Gm-Message-State: AOAM532hdtY4QWh4YDnsRAfngEH50b5YU5/DSdCjyFHCM/14sGly98o2 EfYLE7FXnn53Fp1ko8N7rEYnetu+Zh1LaQ7Zvs71NNXHB3jC/N0zHYuALOFqxQhU1uYi5Azihn2 7mKIL9LRZNczRzz5O7DYmg7nA X-Received: by 2002:a50:9e43:: with SMTP id z61mr8607126ede.278.1634649983165; Tue, 19 Oct 2021 06:26:23 -0700 (PDT) X-Google-Smtp-Source: ABdhPJy62EfSYdgDeaHrlAb3736SelVSwBK7IJhVFYkdE/gexnUl7p1lCZQACzD7HUYMujU/YRH2Pg== X-Received: by 2002:a50:9e43:: with SMTP id z61mr8607094ede.278.1634649982960; Tue, 19 Oct 2021 06:26:22 -0700 (PDT) Received: from krava ([83.240.63.48]) by smtp.gmail.com with ESMTPSA id q14sm10102365eji.63.2021.10.19.06.26.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Oct 2021 06:26:22 -0700 (PDT) Date: Tue, 19 Oct 2021 15:26:21 +0200 From: Jiri Olsa To: Steven Rostedt Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Subject: Re: [PATCH 7/8] ftrace: Add multi direct modify interface Message-ID: References: <20211008091336.33616-1-jolsa@kernel.org> <20211008091336.33616-8-jolsa@kernel.org> <20211014162819.5c85618b@gandalf.local.home> <20211015100509.78d4fb01@gandalf.local.home> <20211018221015.3f145843@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 19, 2021 at 03:19:48PM +0200, Jiri Olsa wrote: > On Mon, Oct 18, 2021 at 10:10:15PM -0400, Steven Rostedt wrote: > > On Sat, 16 Oct 2021 13:39:55 +0200 > > Jiri Olsa wrote: > > > > > On Fri, Oct 15, 2021 at 10:05:09AM -0400, Steven Rostedt wrote: > > > > On Fri, 15 Oct 2021 14:05:25 +0200 > > > > Jiri Olsa wrote: > > > > > > > > > ATM I'm bit stuck on the bpf side of this whole change, I'll test > > > > > it with my other changes when I unstuck myself ;-) > > > > > > > > If you want, I'll apply this as a separate change on top of your patch set. > > > > As I don't see anything wrong with your current code. > > > > > > > > And when you are satisfied with this, just give me a "tested-by" and I'll > > > > push it too. > > > > > > sounds great, thanks > > > jirka > > > > Would you want to ack/review this? > > hum, do you have it in some branch already? I'm getting: > > patching file kernel/trace/ftrace.c > Hunk #1 succeeded at 5521 with fuzz 1 (offset -40 lines). > Hunk #2 FAILED at 5576. > Hunk #3 succeeded at 5557 (offset -44 lines). > 1 out of 3 hunks FAILED -- saving rejects to file kernel/trace/ftrace.c.rej > > > when trying to apply on top of my changes I updated my ftrace/direct branch, it actually still had the previous version.. sorry, perhaps this is the cause of fuzz jirka > > thanks, > jirka > > > > > -- Steve > > > > From: "Steven Rostedt (VMware)" > > Subject: [PATCH] ftrace/direct: Do not disable when switching direct callers > > > > Currently to switch a set of "multi" direct trampolines from one > > trampoline to another, a full shutdown of the current set needs to be > > done, followed by an update to what trampoline the direct callers would > > call, and then re-enabling the callers. This leaves a time when the > > functions will not be calling anything, and events may be missed. > > > > Instead, use a trick to allow all the functions with direct trampolines > > attached will always call either the new or old trampoline while the > > switch is happening. To do this, first attach a "dummy" callback via > > ftrace to all the functions that the current direct trampoline is attached > > to. This will cause the functions to call the "list func" instead of the > > direct trampoline. The list function will call the direct trampoline > > "helper" that will set the function it should call as it returns back to > > the ftrace trampoline. > > > > At this moment, the direct caller descriptor can safely update the direct > > call trampoline. The list function will pick either the new or old > > function (depending on the memory coherency model of the architecture). > > > > Now removing the dummy function from each of the locations of the direct > > trampoline caller, will put back the direct call, but now to the new > > trampoline. > > > > A better visual is: > > > > [ Changing direct call from my_direct_1 to my_direct_2 ] > > > > : > > call my_direct_1 > > > > |||||||||||||||||||| > > vvvvvvvvvvvvvvvvvvvv > > > > : > > call ftrace_caller > > > > : > > [..] > > call ftrace_ops_list_func > > > > ftrace_ops_list_func() > > { > > ops->func() -> direct_helper -> set rax to my_direct_1 or my_direct_2 > > } > > > > call rax (to either my_direct_1 or my_direct_2 > > > > |||||||||||||||||||| > > vvvvvvvvvvvvvvvvvvvv > > > > : > > call my_direct_2 > > > > Link: https://lore.kernel.org/all/20211014162819.5c85618b@gandalf.local.home/ > > > > Signed-off-by: Steven Rostedt (VMware) > > --- > > kernel/trace/ftrace.c | 33 ++++++++++++++++++++------------- > > 1 file changed, 20 insertions(+), 13 deletions(-) > > > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > > index 30120342176e..7ad1e8ae5855 100644 > > --- a/kernel/trace/ftrace.c > > +++ b/kernel/trace/ftrace.c > > @@ -5561,8 +5561,12 @@ EXPORT_SYMBOL_GPL(unregister_ftrace_direct_multi); > > */ > > int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr) > > { > > - struct ftrace_hash *hash = ops->func_hash->filter_hash; > > + struct ftrace_hash *hash; > > struct ftrace_func_entry *entry, *iter; > > + static struct ftrace_ops tmp_ops = { > > + .func = ftrace_stub, > > + .flags = FTRACE_OPS_FL_STUB, > > + }; > > int i, size; > > int err; > > > > @@ -5572,21 +5576,22 @@ int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr) > > return -EINVAL; > > > > mutex_lock(&direct_mutex); > > - mutex_lock(&ftrace_lock); > > + > > + /* Enable the tmp_ops to have the same functions as the direct ops */ > > + ftrace_ops_init(&tmp_ops); > > + tmp_ops.func_hash = ops->func_hash; > > + > > + err = register_ftrace_function(&tmp_ops); > > + if (err) > > + goto out_direct; > > > > /* > > - * Shutdown the ops, change 'direct' pointer for each > > - * ops entry in direct_functions hash and startup the > > - * ops back again. > > - * > > - * Note there is no callback called for @ops object after > > - * this ftrace_shutdown call until ftrace_startup is called > > - * later on. > > + * Now the ftrace_ops_list_func() is called to do the direct callers. > > + * We can safely change the direct functions attached to each entry. > > */ > > - err = ftrace_shutdown(ops, 0); > > - if (err) > > - goto out_unlock; > > + mutex_lock(&ftrace_lock); > > > > + hash = ops->func_hash->filter_hash; > > size = 1 << hash->size_bits; > > for (i = 0; i < size; i++) { > > hlist_for_each_entry(iter, &hash->buckets[i], hlist) { > > @@ -5597,10 +5602,12 @@ int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr) > > } > > } > > > > - err = ftrace_startup(ops, 0); > > + /* Removing the tmp_ops will add the updated direct callers to the functions */ > > + unregister_ftrace_function(&tmp_ops); > > > > out_unlock: > > mutex_unlock(&ftrace_lock); > > + out_direct: > > mutex_unlock(&direct_mutex); > > return err; > > } > > -- > > 2.31.1 > >