From: Oleg Nesterov <oleg@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
"zhangwei(Jovi)" <jovi.zhangwei@huawei.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
stable <stable@vger.kernel.org>
Subject: Re: [PATCH] uprobes: Use synchronize_rcu() not synchronize_sched()
Date: Fri, 10 Aug 2018 13:35:49 +0200 [thread overview]
Message-ID: <20180810113548.GA3677@redhat.com> (raw)
In-Reply-To: <20180809160553.469e1e32@gandalf.local.home>
On 08/09, Steven Rostedt wrote:
>
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -952,7 +952,7 @@ probe_event_disable(struct trace_uprobe *tu, struct trace_event_file *file)
>
> list_del_rcu(&link->list);
> /* synchronize with u{,ret}probe_trace_func */
> - synchronize_sched();
> + synchronize_rcu();
Can't we change uprobe_trace_func() and uretprobe_trace_func() to use
rcu_read_lock_sched() instead? It is more cheap.
Hmm. probe_event_enable() does list_del + kfree on failure, this doesn't
look right... Not only because kfree() can race with list_for_each_entry_rcu(),
we should not put the 1st link on list until uprobe_buffer_enable().
Does the patch below make sense or I am confused?
Oleg.
--- x/kernel/trace/trace_uprobe.c
+++ x/kernel/trace/trace_uprobe.c
@@ -896,8 +896,6 @@ probe_event_enable(struct trace_uprobe *
return -ENOMEM;
link->file = file;
- list_add_tail_rcu(&link->list, &tu->tp.files);
-
tu->tp.flags |= TP_FLAG_TRACE;
} else {
if (tu->tp.flags & TP_FLAG_TRACE)
@@ -909,7 +907,7 @@ probe_event_enable(struct trace_uprobe *
WARN_ON(!uprobe_filter_is_empty(&tu->filter));
if (enabled)
- return 0;
+ goto add;
ret = uprobe_buffer_enable();
if (ret)
@@ -920,7 +918,8 @@ probe_event_enable(struct trace_uprobe *
ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
if (ret)
goto err_buffer;
-
+ add:
+ list_add_tail_rcu(&link->list, &tu->tp.files);
return 0;
err_buffer:
@@ -928,7 +927,6 @@ probe_event_enable(struct trace_uprobe *
err_flags:
if (file) {
- list_del(&link->list);
kfree(link);
tu->tp.flags &= ~TP_FLAG_TRACE;
} else {
next prev parent reply other threads:[~2018-08-10 11:35 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-09 20:05 [PATCH] uprobes: Use synchronize_rcu() not synchronize_sched() Steven Rostedt
2018-08-10 11:35 ` Oleg Nesterov [this message]
2018-08-10 11:42 ` Oleg Nesterov
2018-08-10 12:48 ` Steven Rostedt
2018-08-10 13:36 ` Oleg Nesterov
2018-08-10 13:44 ` Steven Rostedt
2018-08-10 14:06 ` Oleg Nesterov
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