Messages in this thread | | | Date | Sun, 12 Jun 2011 22:31:58 -0700 | Subject | Re: [PATCH 08/10] NOTIFIER: Take over TIF_MCE_NOTIFY and implement task return notifier | From | Tony Luck <> |
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On Sun, Jun 12, 2011 at 3:38 PM, Borislav Petkov <bp@amd64.org> wrote: > On Thu, Jun 09, 2011 at 05:36:42PM -0400, Luck, Tony wrote: >> From: Tony Luck <tony.luck@intel.com> >> >> Existing user return notifier mechanism is designed to catch a specific >> cpu just as it returns to run any task in user mode. We also need a >> mechanism to catch a specific task. > > Why do we need that? I mean, in the remaining patches we end up either > running memory_failure() or sending signals to a task. Can't we do it > all in the user return notifier and not have a different notifier for > each policy?
Unless I'm mis-reading the user-return-notifier code, it is possible that we'll context switch before we get to the notifier. At that point the user-return-notifier TIF bit is passed on from our task to the newly run-able task. But our task is still viable, so another cpu could grab it and start running it ... then we have a race ... will the new task that inherited the notifier unmap the page fast enough, or will there be a loud BANG as the original task runs right into the machine check again.
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