Messages in this thread | | | From | Nadav Amit <> | Subject | Re: [PATCH v3 1/7] Fix "x86/alternatives: Lockdep-enforce text_mutex in text_poke*()" | Date | Mon, 5 Nov 2018 18:14:24 +0000 |
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From: Thomas Gleixner Sent: November 4, 2018 at 8:58:20 PM GMT > To: Nadav Amit <namit@vmware.com> > Cc: Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org>, x86@kernel.org>, H. Peter Anvin <hpa@zytor.com>, Borislav Petkov <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>, Jiri Kosina <jkosina@suse.cz>, Andy Lutomirski <luto@kernel.org>, Kees Cook <keescook@chromium.org>, Dave Hansen <dave.hansen@intel.com> > Subject: Re: [PATCH v3 1/7] Fix "x86/alternatives: Lockdep-enforce text_mutex in text_poke*()" > > > On Fri, 2 Nov 2018, Nadav Amit wrote: > >> text_mutex is expected to be held before text_poke() is called, but we >> cannot add a lockdep assertion since kgdb does not take it, and instead >> *supposedly* ensures the lock is not taken and will not be acquired by >> any other core while text_poke() is running. >> >> The reason for the "supposedly" comment is that it is not entirely clear >> that this would be the case if gdb_do_roundup is zero. >> >> Add a comment to clarify this behavior, and restore the assertions as >> they were before the recent commit. > > It restores nothing. It just removes the assertion.
Sorry - wrong commit log. There were no other assertions before.
> >> This partially reverts commit 9222f606506c ("x86/alternatives: >> Lockdep-enforce text_mutex in text_poke*()") > > That opens up the same can of worms again, which took us a while to close.
I’m surprised. This patch only removes one assertion that was added two months ago.
> Can we please instead split out the text_poke() code into a helper function > and have two callers: > > text_poke() which contains the assert > > text_poke_kgdb() which does not
Sure. I will send another version once I realize how to deal with the other concerns that Peter and Andy raised.
Regards, Nadav
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