linux-kernel - Re: [PATCH] perf_counter: cleanup for __perf_event_sched

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <19129.38627.94363.857137@cargo.ozlabs.ibm.com>
Date:	Wed, 23 Sep 2009 13:32:51 +1000
From:	Paul Mackerras <paulus@...ba.org>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf_counter: cleanup for __perf_event_sched_in()

Xiao Guangrong writes:

> I only find three places in __perf_event_sched_in/out, could you tell me
> where is the fourth place?

My mistake, it is just those three.  I saw the list_for_each_entry_rcu
followed by if (event != event->group_leader) in perf_event_init_task
and missed the fact that it is iterating parent_ctx->event_list rather
than parent_ctx->group_list.  But as you point out:

> I also noticed that all group leader is the top level of ctx->group_list,
> if I not missed, the perf_event_init_task() function can be optimized,
> like this:
> 
> int perf_event_init_task(struct task_struct *child)
> {
> 	......
> 	/* We can only look at parent_ctx->group_list to get group leader */
> 	list_for_each_entry_rcu(event, &parent_ctx->event_list, event_entry) {
> 		if (event != event->group_leader)
> 			continue;
> 	......
> 	}
> 	......
> }

we would in fact be better off using group_list rather than event_list
anyway.  That should be safe since we hold parent_ctx->mutex.

> I'll fix those if you are not mind :-)

Please do. :)

Paul.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/