From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Whitehouse Date: Wed, 03 Jun 2009 13:57:55 +0100 Subject: [Cluster-devel] Re: trace: fix multiple use of __print_flags and __print_symbolic In-Reply-To: <4A26474C.1000900@cn.fujitsu.com> References: <1244019900.29604.588.camel@localhost.localdomain> <4A26474C.1000900@cn.fujitsu.com> Message-ID: <1244033875.29604.599.camel@localhost.localdomain> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Hi On Wed, 2009-06-03 at 17:50 +0800, Li Zefan wrote: > Steven Whitehouse wrote: > > When using multiple calls to __print_symbolic and __print_flags in > > the same tracer, I noticed that the output was incorrect. I think > > the following patch is the correct fix (it works for me) but please > > check it carefully since I'm not that familiar with this code, > > and I may well have made a mistake somewhere. > > > > I don't see there's bug in __print_symbolic() or __print_flags(): > > enum print_line_t > ftrace_raw_output_##call(struct trace_iterator *iter, int flags) > { > ... > p = &get_cpu_var(ftrace_event_seq); > /* here we call ftrace_print_flags_seq(p, ...) */ > ret = trace_seq_printf(s, #call ": " print); > put_cpu(); > ... > } > > ftrace_event_seq is percpu data, and here is used with preempt-disabled, > so there shouldn't be problem of concurrent accessing. > I've double checked this now, and I'm seeing results like: glock_workqueue-2482 [001] 809.956985: gfs2_glock_state_change: 8.7 glock 2:33119 state EX => EX tgt:EX dmt:EX flags:EX glock_workqueue-2482 [001] 809.957155: gfs2_glock_state_change: 8.7 glock 2:33119 state NL => NL tgt:NL dmt:NL flags:NL glock_workqueue-2482 [001] 809.959473: gfs2_glock_state_change: 8.7 glock 1:2 state NL => NL tgt:NL dmt:NL flags:NL glock_workqueue-2482 [001] 809.959556: gfs2_glock_state_change: 8.7 glock 2:33119 state EX => EX tgt:EX dmt:EX flags:EX glock_workqueue-2482 [001] 810.008773: gfs2_glock_state_change: 8.7 glock 1:0 state EX => EX tgt:EX dmt:EX flags:EX without the patch, which is clearly wrong, Steve.