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From:   "Schmid, Carsten" <Carsten_Schmid@mentor.com>
To:     Wei Yang <richard.weiyang@gmail.com>
CC:     Linus Torvalds <torvalds@linux-foundation.org>,
        "bp@suse.de" <bp@suse.de>,
        "dan.j.williams@intel.com" <dan.j.williams@intel.com>,
        "mingo@kernel.org" <mingo@kernel.org>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "bhelgaas@google.com" <bhelgaas@google.com>,
        "osalvador@suse.de" <osalvador@suse.de>,
        "rdunlap@infradead.org" <rdunlap@infradead.org>,
        "richardw.yang@linux.intel.com" <richardw.yang@linux.intel.com>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        Hans de Goede <hdegoede@redhat.com>
Subject: AW: [PATCH v2] kernel/resource.c: invalidate parent when freed
 resource has childs
Thread-Topic: [PATCH v2] kernel/resource.c: invalidate parent when freed
 resource has childs
Thread-Index: AQHVUq5kcb5Ex7JpNUSktSjVjdFue6b6xMYAgAEUHnCAAESkAIAAERsQ
Date:   Thu, 15 Aug 2019 13:17:01 +0000
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> My gut feeling is this is the problem from mal-functional driver, e.g.
> xhci-hcd. We do our best to protect core kernel from it instead of do the
> cleanup for it.
Agree.
My intention wasn't to fix mal-functional driver, but to give it a hint
that it's doing something wrong.
(In the xhci-hcd case the patch indirectly avoids the later use-after-free in driver,
 a nice side effect here)

I think the same what Linus meant with
> I'm less interested in the xhci-hcd case - which I certainly *hope* is
> fixed already? - than in "if this happens somewhere else".
What about giving only a WARN_ONCE?
Wouldn't hurt but notice developers and ease bug hunting.
Would be fine for me too.
Finally, i also could put the patch in a private branch named "useful_patches" ;-)
but then the community won't benefit.

> 
> So my suggestion is to look into why xhci-hcd behave like this and fix that.
> 
xhci-hcd fix proposal @ Hans de Goede already.

Best regards
Carsten