linux-kernel - Re: [PATCH 3/3] ftrace: add ability to only trace swapper tasks

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]

Date:	Fri, 5 Dec 2008 07:23:07 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	containers@...ts.osdl.org,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 3/3] ftrace: add ability to only trace swapper tasks


On Thu, 4 Dec 2008, Eric W. Biederman wrote:

> Steven Rostedt <rostedt@...dmis.org> writes:
> 
> > On Thu, 4 Dec 2008, Eric W. Biederman wrote:
> >> 
> >> Right.  I simply meant most of the
> >> if (likely(p->pid)) conditional except for the counts is pretty much a don't
> >> care.  Keeping the idle tasks off of the process list and out of the counts
> >> is useful.
> >> 
> >> For this particular case what problem did you see with calling attach_pid
> >> with PIDTYPE_PID on init_struct_pid?
> >
> > On boot up, the CPU 0 idle task is attached to init_struct_pid, and not 
> > the others. If you do a "attach_pid" on the next idle task that is created, 
> > it will become the attched process, bumping off CPU 0's idle task from the 
> > init_struct_pid.
> 
> It should form a linked list.  For other pid types we don't have a problem.

Other pids get allocated per task. In the beginning of copy_process we 
have:

        if (pid != &init_struct_pid) {
                retval = -ENOMEM;
                pid = alloc_pid(task_active_pid_ns(p));

Where alloc_pid allocates a pid structure. But this is only done if it is
not a swapper task.

> 
> > When doing the code you suggested, I end up with only marking the last 
> > idle task to be created.
> 
> Odd. It is all a linked list through the task structures.
> I'm guessing the initialization isn't quite right.
> 
> Weird.  

Do I need to change the loop to do_each_pid_thread?

I'll try that later today.

-- Steve

--
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/