Messages in this thread | | | Subject | Re: [PATCH] mm/slub: use WARN_ON() for some slab errors | From | Miles Chen <> | Date | Tue, 22 Jan 2019 12:14:35 +0800 |
| |
On Mon, 2019-01-21 at 22:02 +0000, Christopher Lameter wrote: > On Mon, 21 Jan 2019, miles.chen@mediatek.com wrote: > > > From: Miles Chen <miles.chen@mediatek.com> > > > > When debugging with slub.c, sometimes we have to trigger a panic in > > order to get the coredump file. To do that, we have to modify slub.c and > > rebuild kernel. To make debugging easier, use WARN_ON() for these slab > > errors so we can dump stack trace by default or set panic_on_warn to > > trigger a panic. > > These locations really should dump stack and not terminate. There is > subsequent processing that should be done.
Understood. We should not terminate the process for normal case. The change only terminate the process when panic_on_warn is set.
> Slub terminates by default. The messages you are modifying are only > enabled if the user specified that special debugging should be one > (typically via a kernel parameter slub_debug).
I'm a little bit confused about this: Do you mean that I should use the following approach?
1. Add a special debugging flag (say SLAB_PANIC_ON_ERROR) and call panic() by:
if (s->flags & SLAB_PANIC_ON_ERROR) panic("slab error");
2. The SLAB_PANIC_ON_ERROR should be set by slub_debug param.
> It does not make sense to terminate the process here.
Thanks for you comment. Sometimes it's useful to trigger a panic and get its coredump file before any restore/reset processing because we can exam the unmodified data in the coredump file with this approach.
I added BUG() for the slab errors in internal branches for a few years and it does help for both software issues and bit flipping issues. It's a quite useful in developing stage.
cheers, Miles
| |