Messages in this thread | | | Subject | Re: [RFC] logdev debugging memory device for tough to debug areas | From | Steven Rostedt <> | Date | Tue, 29 Mar 2005 06:53:30 -0500 |
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On Tue, 2005-03-29 at 11:07 +0200, Ingo Molnar wrote: > * Steven Rostedt <rostedt@goodmis.org> wrote: > > > I've created a tracing tool several years ago for my master's thesis > > against the 2.2 kernel and onto the 2.4 kernel. I'm currently using > > this in the 2.6 kernel to debug some customizations against Ingo's RT > > kernel. > > neat. It seems there's some overlap with relayfs, which is in -mm > currently: > > http://kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.12-rc1/2.6.12-rc1-mm3/broken-out/relayfs.patch >
Thanks Ingo, I didn't know about this. I'll look into it further when I have more time, and maybe my tools already implement things that need to be done in here, and I can port them (if they're interested). I first wrote this back in 1998 or 1999 and have added on since then. So it is pretty mature. Unfortunately I still had to clean it up for the post. It was only for my personal use till someone mentioned to me that I should share it.
Also, I'm almost done adding the pending owner work against .41-11. I see you now have 41-13, and if you already implemented it, let me know. I've been fighting your deadlock detection to make sure it works with the changes. Then finally I found a race condition that I'm solving.
To have a task take back the ownership, I had the stealer call task_blocks_on_lock on the task that it stole it from. To get this to work, when a task is given the pending ownership, it doesn't NULL the blocked_on at that point (although the waiter->task is set to NULL). But this gives the race condition in pi_setprio where it checks for p->blocked_on still exists. Reason is that I don't want the waking up of a process to call any more locks. To solve this, I had to (and this is what I don't like right now) add another flag for the process called PF_BLOCKED. So that this can tell the pi_setprio when to stop. This flag is set in task_blocks_on_lock and cleared in pick_new_owner where the setting of blocked_on to NULL use to be.
Unless you already implemented this, I'll have a patch for you to look at later today, and you can then (if you want) critique it :-)
-- Steve
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