[Xen-changelog] [xen master] gnttab: drop useless locking

[patchbot@xxxxxxx]

commit 25726f4269c742fd41ee0df733bbe7a3a05339ac
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Aug 16 10:56:23 2017 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Aug 16 10:56:23 2017 +0200

    gnttab: drop useless locking
    
    Holding any lock while accessing the maptrack entry fields is
    pointless, as these entries are protected by their associated active
    entry lock (which is being acquired later, before re-validating the
    fields read without holding the lock).
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/common/grant_table.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index 56082d8..5e578c6 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -1143,19 +1143,14 @@ __gnttab_unmap_common(
     smp_rmb();
     map = &maptrack_entry(lgt, op->handle);
 
-    grant_read_lock(lgt);
-
     if ( unlikely(!read_atomic(&map->flags)) )
     {
-        grant_read_unlock(lgt);
         gdprintk(XENLOG_INFO, "Zero flags for handle %#x\n", op->handle);
         op->status = GNTST_bad_handle;
         return;
     }
 
     dom = map->domid;
-    grant_read_unlock(lgt);
-
     if ( unlikely((rd = rcu_lock_domain_by_id(dom)) == NULL) )
     {
         /* This can happen when a grant is implicitly unmapped. */
--
generated by git-patchbot for /home/xen/git/xen.git#master

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