Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754188Ab3GXUOB (ORCPT ); Wed, 24 Jul 2013 16:14:01 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:7935 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754007Ab3GXUNS (ORCPT ); Wed, 24 Jul 2013 16:13:18 -0400 X-Authority-Analysis: v=2.0 cv=P6i4d18u c=1 sm=0 a=Sro2XwOs0tJUSHxCKfOySw==:17 a=Drc5e87SC40A:10 a=Qu6ugZQ4bf4A:10 a=5SG0PmZfjMsA:10 a=IkcTkHD0fZMA:10 a=meVymXHHAAAA:8 a=KGjhK52YXX0A:10 a=HnnTJNGInn0A:10 a=20KFwNOVAAAA:8 a=A-5jg6PAATL5xQ1MlGkA:9 a=QEXdDO2ut3YA:10 a=jEp0ucaQiEUA:10 a=Sro2XwOs0tJUSHxCKfOySw==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 67.255.60.225 Message-ID: <1374696796.3356.162.camel@gandalf.local.home> Subject: Re: [PATCH 1/6] tracing: Turn event/id->i_private into call->event.type From: Steven Rostedt To: Oleg Nesterov Cc: Masami Hiramatsu , Alexander Z Lam , Arnaldo Carvalho de Melo , David Sharp , Frederic Weisbecker , Ingo Molnar , Peter Zijlstra , Srikar Dronamraju , Vaibhav Nagarnaik , "zhangwei(Jovi)" , linux-kernel@vger.kernel.org Date: Wed, 24 Jul 2013 16:13:16 -0400 In-Reply-To: <20130723205909.GA9055@redhat.com> References: <20130723205909.GA9055@redhat.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.4-3 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3288 Lines: 109 On Tue, 2013-07-23 at 22:59 +0200, Oleg Nesterov wrote: > event_id_read() is racy, ftrace_event_call can be already freed > by trace_remove_event_call() callers. > > Change event_create_dir() to pass "data = call->event.type", this > is all event_id_read() needs. ftrace_event_id_fops no longer needs > tracing_open_generic(). > > We add the new helper, event_file_data(), to read ->i_private, it > will have more users. > > Note: currently ACCESS_ONCE() and "id != 0" check are not needed, > but we are going to change event_remove/rmdir to clear ->i_mutex. We are changing i_mutex or i_private? Anyway, this still looks too complex for the id. Just pass the id number to the filp->private_data, and use that. It should never be cleared, and as we are not using any pointers it will always return what the id is/was. Keep tracing_open_generic() and have: event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos) { int id = (int)(unsigned long)filp->private_data; char buf[32]; int len; if (*ppos) return 0; len = sprintf(buf, "%d\n", id); return simple_read_from_buffer(ubuf, cnt, ppos, buf, len); } No need for accessing the inode->i_private. -- Steve > > Signed-off-by: Oleg Nesterov > --- > kernel/trace/trace_events.c | 17 ++++++++++++----- > 1 files changed, 12 insertions(+), 5 deletions(-) > > diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c > index 76eed53..77990c4 100644 > --- a/kernel/trace/trace_events.c > +++ b/kernel/trace/trace_events.c > @@ -409,6 +409,11 @@ static void put_system(struct ftrace_subsystem_dir *dir) > mutex_unlock(&event_mutex); > } > > +static void *event_file_data(struct file *filp) > +{ > + return ACCESS_ONCE(file_inode(filp)->i_private); > +} > + > /* > * Open and update trace_array ref count. > * Must have the current trace_array passed to it. > @@ -946,14 +951,17 @@ static int trace_format_open(struct inode *inode, struct file *file) > static ssize_t > event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos) > { > - struct ftrace_event_call *call = filp->private_data; > + int id = (long)event_file_data(filp); > char buf[32]; > int len; > > if (*ppos) > return 0; > > - len = sprintf(buf, "%d\n", call->event.type); > + if (unlikely(!id)) > + return -ENODEV; > + > + len = sprintf(buf, "%d\n", id); > return simple_read_from_buffer(ubuf, cnt, ppos, buf, len); > } > > @@ -1240,7 +1248,6 @@ static const struct file_operations ftrace_event_format_fops = { > }; > > static const struct file_operations ftrace_event_id_fops = { > - .open = tracing_open_generic, > .read = event_id_read, > .llseek = default_llseek, > }; > @@ -1488,8 +1495,8 @@ event_create_dir(struct dentry *parent, > > #ifdef CONFIG_PERF_EVENTS > if (call->event.type && call->class->reg) > - trace_create_file("id", 0444, file->dir, call, > - id); > + trace_create_file("id", 0444, file->dir, > + (void *)(long)call->event.type, id); > #endif > > /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/