This moves a kfree outside a spinlock to help scaling on larger (512 core)
systems.  This should be some relief until we can move the section to use
the rcu.

I ran a simple test which just reads from /proc/cpuinfo.
Lower is better, as you can see the worst case scenario is improved.

        baseline        moved kfree
tasks   read-sec        read-sec
1       0.0141          0.0141
2       0.0140          0.0140
4       0.0140          0.0141
8       0.0145          0.0145
16      0.0553          0.0548
32      0.1688          0.1622
64      0.5017          0.3856
128     1.7005          0.9710
256     5.2513          2.6519
512     8.0529          6.2976

Cc: "Eric W. Biederman" <ebied...@xmission.com> 
Cc: Andrew Morton <a...@linux-foundation.org> 
Cc: Alexander Viro <v...@zeniv.linux.org.uk>
Cc: David Woodhouse <dw...@infradead.org>
Cc: <sta...@vger.kernel.org>
Acked-by: Alexey Dobriyan <adobri...@gmail.com>
Signed-off-by: Nathan Zimmer <nzim...@sgi.com>
---
 fs/proc/inode.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 439ae688..863608b 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -403,11 +403,10 @@ static int proc_reg_release(struct inode *inode, struct 
file *file)
        }
        pde->pde_users++;
        release = pde->proc_fops->release;
-       if (pdeo) {
+       if (pdeo)
                list_del(&pdeo->lh);
-               kfree(pdeo);
-       }
        spin_unlock(&pde->pde_unload_lock);
+       kfree(pdeo);
 
        if (release)
                rv = release(inode, file);
-- 
1.8.1.2

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