Messages in this thread | | | Date | Wed, 20 Feb 2013 16:17:39 -0800 | Subject | Re: [PATCH v4] lockdep: check that no locks held at freeze time | From | Mandeep Singh Baines <> |
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On Wed, Feb 20, 2013 at 3:24 PM, Andrew Morton <akpm@linux-foundation.org> wrote: > On Wed, 20 Feb 2013 15:17:16 -0800 > Mandeep Singh Baines <msb@chromium.org> wrote: > >> We shouldn't try_to_freeze if locks are held. >> >> ... >> >> @@ -43,6 +44,9 @@ extern void thaw_kernel_threads(void); >> >> + if (!(current->flags & PF_NOFREEZE)) >> + debug_check_no_locks_held(current, >> + >> "lock held while trying to freeze"); >> ... >> >> + debug_check_no_locks_held(tsk, "lock held at task exit time"); > > There doesn't seem much point in adding the `msg' to > debug_check_no_locks_held() - the dump_stack() in > print_held_locks_bug() will tell us the same thing. Maybe just change
dump_stack() can be confusing when there is inlining. On occasion I've looked at the wrong mutex_lock, for example, when there was another mutex_lock that was inlined. Of course, you can start objdump and verify the offsets. But that requires that you have the object file. You could have a try_to_freeze added to do_exit. I was thinking of adding another locks_held in the return from syscall path.
How about if we did some inlining and printed out the function, file and line number where the check was placed:
#define debug_check_no_locks_held() do { \ if (unlikely(current->lockdep_depth > 0)) { \ printk("BUG: locks helds at %s:%d/%s()!\n", __FILE__, __LINE__, __func__); \ print_held_locks_bug(); \ } \ } while (0)
That we avoid any potential confusion.
> the print_held_locks_bug() messages so they stop assuming they were > called from do_exit()? > > Also, I wonder if the `tsk' arg is needed. In both callers > tsk==current. Is it likely that we'll ever call > debug_check_no_locks_held() for any task other than `current'? >
I agree. I'll add that change to the patch once we decide what to about msg.
Regards, Mandeep
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