diff options
author | Hugh Dickins <hugh@veritas.com> | 2005-11-07 14:09:01 -0800 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2005-11-07 14:09:01 -0800 |
commit | dedeb0029b9c83420fc1337d4ee53daa7b2a0ad4 (patch) | |
tree | d87e66e1d6240cd412c20ecbc12f5b810c9807e4 /kernel/fork.c | |
parent | b8ae48656db860d4c83a29aa7b0588fc89361935 (diff) |
[SPARC64] mm: context switch ptlock
sparc64 is unique among architectures in taking the page_table_lock in
its context switch (well, cris does too, but erroneously, and it's not
yet SMP anyway).
This seems to be a private affair between switch_mm and activate_mm,
using page_table_lock as a per-mm lock, without any relation to its uses
elsewhere. That's fine, but comment it as such; and unlock sooner in
switch_mm, more like in activate_mm (preemption is disabled here).
There is a block of "if (0)"ed code in smp_flush_tlb_pending which would
have liked to rely on the page_table_lock, in switch_mm and elsewhere;
but its comment explains how dup_mmap's flush_tlb_mm defeated it. And
though that could have been changed at any time over the past few years,
now the chance vanishes as we push the page_table_lock downwards, and
perhaps split it per page table page. Just delete that block of code.
Which leaves the mysterious spin_unlock_wait(&oldmm->page_table_lock)
in kernel/fork.c copy_mm. Textual analysis (supported by Nick Piggin)
suggests that the comment was written by DaveM, and that it relates to
the defeated approach in the sparc64 smp_flush_tlb_pending. Just delete
this block too.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r-- | kernel/fork.c | 7 |
1 files changed, 0 insertions, 7 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index efac2c58ec7..158710d2256 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -470,13 +470,6 @@ static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) if (clone_flags & CLONE_VM) { atomic_inc(&oldmm->mm_users); mm = oldmm; - /* - * There are cases where the PTL is held to ensure no - * new threads start up in user mode using an mm, which - * allows optimizing out ipis; the tlb_gather_mmu code - * is an example. - */ - spin_unlock_wait(&oldmm->page_table_lock); goto good_mm; } |