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| author | Andrea Arcangeli <aarcange@redhat.com> | 2020-02-03 12:31:56 -0500 |
|---|---|---|
| committer | Andrea Arcangeli <aarcange@redhat.com> | 2023-11-11 22:03:37 -0500 |
| commit | e9720aeb58674c615f9aa3c4edb96b6777b7748b (patch) | |
| tree | 33d430bb7b05c9551d12457aacbbac7153dc7d11 | |
| parent | 4ea2a9ff98ac80bc096728c922ccf70c6d2ff7a1 (diff) | |
| download | aa-e9720aeb58674c615f9aa3c4edb96b6777b7748b.tar.gz | |
mm: use_mm: fix for arches checking mm_users to optimize TLB flushes
alpha, ia64, mips, powerpc, sh, sparc are relying on a check on
mm->mm_users to know if they can skip some remote TLB flushes for
single threaded processes.
Most callers of kthread_use_mm() tend to invoke mmget_not_zero() or
get_task_mm() before kthread_use_mm() to ensure the mm will remain
alive in between kthread_use_mm() and kthread_unuse_mm().
Some callers however don't increase mm_users and they instead rely on
serialization in __mmput() to ensure the mm will remain alive in
between kthread_use_mm() and kthread_unuse_mm(). Not increasing
mm_users during kthread_use_mm() is however unsafe for aforementioned
arch TLB flushes optimizations. So either mmget()/mmput() should be
added to the problematic callers of
kthread_use_mm()/kthread_unuse_mm() or we can embed them in
kthread_use_mm()/kthread_unuse_mm() which is more robust.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
| -rw-r--r-- | kernel/kthread.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c index e319a1b62586e9..22641a70cc0313 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -1359,6 +1359,7 @@ void kthread_use_mm(struct mm_struct *mm) mmgrab(mm); tsk->active_mm = mm; } + mmget(mm); tsk->mm = mm; membarrier_update_current_mm(mm); switch_mm_irqs_off(active_mm, mm, tsk); @@ -1399,6 +1400,8 @@ void kthread_unuse_mm(struct mm_struct *mm) force_uaccess_end(to_kthread(tsk)->oldfs); + mmput(mm); + task_lock(tsk); /* * When a kthread stops operating on an address space, the loop |