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Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vWFli-00000008fvE-15dS; Thu, 18 Dec 2025 15:18:18 +0000 Received: from smtprelay0015.hostedemail.com ([216.40.44.15] helo=relay.hostedemail.com) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vWFlf-00000008ftp-0oib for linux-arm-kernel@lists.infradead.org; Thu, 18 Dec 2025 15:18:16 +0000 Received: from omf03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 698F512E4C; Thu, 18 Dec 2025 15:18:07 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf03.hostedemail.com (Postfix) with ESMTPA id ABF8A6000C; Thu, 18 Dec 2025 15:18:04 +0000 (UTC) Date: Thu, 18 Dec 2025 10:19:42 -0500 From: Steven Rostedt To: Jiri Olsa Cc: Steven Rostedt , Florent Revest , Mark Rutland , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Menglong Dong , Song Liu Subject: Re: [PATCHv5 bpf-next 6/9] ftrace: Add update_ftrace_direct_mod function Message-ID: <20251218101942.0716efd6@gandalf.local.home> In-Reply-To: <20251215211402.353056-7-jolsa@kernel.org> References: <20251215211402.353056-1-jolsa@kernel.org> <20251215211402.353056-7-jolsa@kernel.org> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspamout06 X-Rspamd-Queue-Id: ABF8A6000C X-Stat-Signature: 7stoz3y9s7gbc4gkicouzdj7p4f5jkai X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX18Tawb5aeJtZNDj3eiQyPJECxVNSgJGjLo= X-HE-Tag: 1766071084-610297 X-HE-Meta: U2FsdGVkX1+XAMvJSK/Fo4/cUd56YAbeR4EMtxvTGxe6O5eiPBzwZZQW8AjtW8GvcqRXaAi4Xg0Dfvb0qmXfsZLi2ZL09yQG6rNuFLlECwO2WvT+949txinB85A5fYnB02qTqj7gtGAxxhgGPNrqLC9pyVnRe33f2Rk/S9T02jpAO7kSFrZ8DDy98lJe1FxTGRbWK8qJAV7KjclFuPIKC3I/4QM2Re8ZpHqBQRF7CT9qYdlEEZFjrYgjNEZdGEQrSeP36Bm9+ENQRURwkY1X6RLmM5CeZwCBC3eFkBqHvp8NBDWiEu8ngW5hNYYU4tHuxg2zp3RSXNQ7DBGBfQihaUSvhWpda+YW X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251218_071815_299339_98CE7B17 X-CRM114-Status: GOOD ( 23.65 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 15 Dec 2025 22:13:59 +0100 Jiri Olsa wrote: > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index 48dc0de5f2ce..95a38fb18ed7 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -6489,6 +6489,78 @@ int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash) > return err; > } > Kerneldoc needed. > +int update_ftrace_direct_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, bool do_direct_lock) > +{ > + struct ftrace_func_entry *entry, *tmp; > + static struct ftrace_ops tmp_ops = { > + .func = ftrace_stub, > + .flags = FTRACE_OPS_FL_STUB, > + }; > + struct ftrace_hash *orig_hash; > + unsigned long size, i; > + int err = -EINVAL; > + > + if (!hash_count(hash)) > + return -EINVAL; > + if (check_direct_multi(ops)) > + return -EINVAL; > + if (!(ops->flags & FTRACE_OPS_FL_ENABLED)) > + return -EINVAL; > + if (direct_functions == EMPTY_HASH) > + return -EINVAL; > + > + if (do_direct_lock) > + mutex_lock(&direct_mutex); This optional taking of the direct_mutex lock needs some serious rationale and documentation. > + > + orig_hash = ops->func_hash ? ops->func_hash->filter_hash : NULL; > + if (!orig_hash) > + goto unlock; > + > + /* 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_nolock(&tmp_ops); > + if (err) > + goto unlock; > + > + /* > + * Call __ftrace_hash_update_ipmodify() here, so that we can call > + * ops->ops_func for the ops. This is needed because the above > + * register_ftrace_function_nolock() worked on tmp_ops. > + */ > + err = __ftrace_hash_update_ipmodify(ops, orig_hash, orig_hash, true); > + if (err) > + goto out; > + > + /* > + * Now the ftrace_ops_list_func() is called to do the direct callers. > + * We can safely change the direct functions attached to each entry. > + */ > + mutex_lock(&ftrace_lock); I'm going to need some time staring at this code. It looks like it may be relying on some internals here. -- Steve > + > + size = 1 << hash->size_bits; > + for (i = 0; i < size; i++) { > + hlist_for_each_entry(entry, &hash->buckets[i], hlist) { > + tmp = __ftrace_lookup_ip(direct_functions, entry->ip); > + if (!tmp) > + continue; > + tmp->direct = entry->direct; > + } > + } > + > + mutex_unlock(&ftrace_lock); > + > +out: > + /* Removing the tmp_ops will add the updated direct callers to the functions */ > + unregister_ftrace_function(&tmp_ops); > + > +unlock: > + if (do_direct_lock) > + mutex_unlock(&direct_mutex); > + return err; > +} > + > #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */ > > /**