Messages in this thread | | | From | Joel Fernandes <> | Date | Sat, 2 Sep 2023 22:05:08 -0400 | Subject | Re: [PATCH 2/2] rcu: Dump vmalloc memory info safely |
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On Sat, Sep 2, 2023 at 10:03 PM Joel Fernandes <joel@joelfernandes.org> wrote: > > On Sat, Sep 2, 2023 at 9:28 PM Andrew Morton <akpm@linux-foundation.org> wrote: > > > > On Wed, 30 Aug 2023 11:04:00 +0000 "Joel Fernandes (Google)" <joel@joelfernandes.org> wrote: > > > > > Currently, for double invoke call_rcu(), will dump rcu_head objects > > > memory info, if the objects is not allocated from the slab allocator, > > > the vmalloc_dump_obj() will be invoke and the vmap_area_lock spinlock > > > need to be held, since the call_rcu() can be invoked in interrupt context, > > > therefore, there is a possibility of spinlock deadlock scenarios. > > > > > > And in Preempt-RT kernel, the rcutorture test also trigger the following > > > lockdep warning: > > > > "possibility of deadlock" sounds like something -stable kernels would > > like to have fixed. > > > > Did you consider the desirability of a -stable backport? > > > > If so, are we able to identify a suitable Fixes: target? > > Good point, it should be: > Fixes: 98f180837a89 ("mm: Make mem_dump_obj() handle vmalloc() memory") > > I am currently reworking the patch as Vlad was also concerned about > (the existing) issue of accessing vm_struct fields without holding the > lock [1]. > > I will add this fixes tag to both patches for the v3 on the respin. >
Sigh, I missed sharing the link to [1]: [1] https://lore.kernel.org/all/20230901003321.GA3389909@google.com/
thanks,
- Joel
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