On 07/10/2016 06:04 AM, yhb@xxxxxxxxxxxxx wrote:
Subject: [PATCH] MIPS: We need to clear MMU contexts of all other processes
when asid_cache(cpu) wraps to 0.
Suppose that asid_cache(cpu) wraps to 0 every n days.
case 1:
(1)Process 1 got ASID 0x101.
(2)Process 1 slept for n days.
(3)asid_cache(cpu) wrapped to 0x101, and process 2 got ASID 0x101.
(4)Process 1 is woken,and ASID of process 1 is same as ASID of process 2.
case 2:
(1)Process 1 got ASID 0x101 on CPU 1.
(2)Process 1 migrated to CPU 2.
(3)Process 1 migrated to CPU 1 after n days.
(4)asid_cache on CPU 1 wrapped to 0x101, and process 2 got ASID 0x101.
(5)Process 1 is scheduled, and ASID of process 1 is same as ASID of process 2.
So we need to clear MMU contexts of all other processes when asid_cache(cpu) wraps to 0.
Signed-off-by: yhb <yhb@xxxxxxxxxxxxx>
I think a more clear description should be given here - there is no
indication that wrap happens over 32bit integer.
And taking into account "n days" frequency - can we just kill all local
ASIDs in all processes (additionally to local_flush_tlb_all) and enforce
reassignment if wrap happens? It should be a very rare event, you are
first to hit this.
It seems to be some localized stuff in get_new_mmu_context() instead of
widespread patching.
- Leonid.
