The MMU context_lock can be taken from switch_mm() while the
rq->lock is held. The rq->lock can also be taken from interrupts,
thus if we get interrupted in destroy_context() with the context
lock held and that interrupt tries to take the rq->lock, there's
a possible deadlock scenario with another CPU having the rq->lock
and calling switch_mm() which takes our context lock.
The fix is to always ensure interrupts are off when taking our
context lock. The switch_mm() path is already good so this fixes
the destroy_context() path.
While at it, turn the context lock into a new style spinlock.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This patch fixes a couple of issues that can happen as a result
of steal_context() dropping the context_lock when all possible
PIDs are ineligible for stealing (hopefully an extremely hard to
hit occurence).
This case exposes the possibility of a stale context_mm[] entry
to be seen since destroy_context() doesn't clear it and the free
map isn't re-tested. It also means steal_context() will not notice
a context freed while the lock was help, thus possibly trying to
steal a context when a free one was available.
This fixes it by always returning to the caller from steal_context
when it dropped the lock with a return value that causes the
caller to re-samble the number of free contexts, along with
properly clearing the context_mm[] array for destroyed contexts.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
The recent rework of the MMU PID handling for non-hash CPUs has a
subtle bug in the !SMP "optimized" variant of the PID stealing
function. It clears the PID in the mm context before it calls
local_flush_tlb_mm(). However, the later will not flush anything
if the PID in the context is clear...
Signed-off-by: Hideo Saito <hsaito.ppc@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Makes code futureproof against the impending change to mm->cpu_vm_mask.
It's also a chance to use the new cpumask_ ops which take a pointer
(the older ones are deprecated, but there's no hurry for arch code).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This makes the MMU context code used for CPUs with no hash table
(except 603) dynamically allocate the various maps used to track
the state of contexts.
Only the main free map and CPU 0 stale map are allocated at boot
time. Other CPU maps are allocated when those CPUs are brought up
and freed if they are unplugged.
This also moves the initialization of the MMU context management
slightly later during the boot process, which should be fine as
it's really only needed when userland if first started anyways.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This reworks the context management code used by 4xx,8xx and
freescale BookE. It adds support for SMP by implementing a
concept of stale context map to lazily flush the TLB on
processors where a context may have been invalidated. This
also contains the ground work for generalizing such lazy TLB
flushing by just picking up a new PID and marking the old one
stale. This will be implemented later.
This is a first implementation that uses a global spinlock.
Ideally, we should try to get at least the fast path (context ID
already assigned) lockless or limited to a per context lock,
but for now this will do.
I tried to keep the UP case reasonably simple to avoid adding
too much overhead to 8xx which does a lot of context stealing
since it effectively has only 16 PIDs available.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This splits the mmu_context handling between 32-bit hash based
processors, 64-bit hash based processors and everybody else. This is
preliminary work for adding SMP support for BookE processors.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
