linux-kernel - Re: [PATCH 3/4] locking/lockdep: Reduce space occupied by stack traces

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Date:   Tue, 23 Jul 2019 21:56:10 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Bart Van Assche <bvanassche@....org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will.deacon@....com>,
        Yuyang Du <duyuyang@...il.com>,
        Waiman Long <longman@...hat.com>
Subject: Re: [PATCH 3/4] locking/lockdep: Reduce space occupied by stack
 traces

On Mon, Jul 22, 2019 at 11:24:42AM -0700, Bart Van Assche wrote:
> Although commit 669de8bda87b ("kernel/workqueue: Use dynamic lockdep keys
> for workqueues") unregisters dynamic lockdep keys when a workqueue is
> destroyed, a side effect of that commit is that all stack traces
> associated with the lockdep key are leaked when a workqueue is destroyed.
> Fix this by storing each unique stack trace once. Other changes in this
> patch are:
> - Use NULL instead of { .nr_entries = 0 } to represent 'no trace'.
> - Store a pointer to a stack trace in struct lock_class and struct
>   lock_list instead of storing 'nr_entries' and 'offset'.
> 
> This patch avoids that the following program triggers the "BUG:
> MAX_STACK_TRACE_ENTRIES too low!" complaint:


Does this also fix any of the other bugs listed at
https://lore.kernel.org/lkml/20190710055838.GC2152@sol.localdomain/
?

BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!
BUG: MAX_LOCKDEP_CHAINS too low!
BUG: MAX_LOCK_DEPTH too low! (2)
BUG: MAX_LOCKDEP_ENTRIES too low!

> 
> 	#include <fcntl.h>
> 	#include <unistd.h>
> 
> 	int main()
> 	{
> 		for (;;) {
> 			int fd = open("/dev/infiniband/rdma_cm", O_RDWR);
> 			close(fd);
> 		}
> 	}
> 
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Yuyang Du <duyuyang@...il.com>
> Cc: Waiman Long <longman@...hat.com>
> Reported-by: Eric Biggers <ebiggers@...nel.org>

Can you please add:

Reported-by: syzbot+6f39a9deb697359fe520@...kaller.appspotmail.com

Thanks,

- Eric