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| author |   Eric Dumazet <eric.dumazet@gmail.com> | 2011-07-31 22:09:25 -0700 |
|---|---|---|
| committer |   Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2011-09-28 21:38:33 -0700 |
| commit | d322f45ceed525daa9401154590bbae3222cfefb (patch) | |
| tree | f9c2534f0b10d149af2f899ad200125dc29f631b /include/linux/rcupdate.h | |
| parent | rcu: Make rcu_implicit_dynticks_qs() locals be correct size (diff) | |
| download | linux-dev-d322f45ceed525daa9401154590bbae3222cfefb.tar.xz linux-dev-d322f45ceed525daa9401154590bbae3222cfefb.zip | |
rcu: Make rcu_assign_pointer() unconditionally insert a memory barrier
Recent changes to gcc give warning messages on rcu_assign_pointers()'s
checks that allow it to determine when it is OK to omit the memory
barrier. Stephen Hemminger tried a number of gcc tricks to silence
this warning, but #pragmas and CPP macros do not work together in the
way that would be required to make this work.
However, we now have RCU_INIT_POINTER(), which already omits this
memory barrier, and which therefore may be used when assigning NULL to
an RCU-protected pointer that is accessible to readers. This commit
therefore makes rcu_assign_pointer() unconditionally emit the memory
barrier.
Reported-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'include/linux/rcupdate.h')
| -rw-r--r-- | include/linux/rcupdate.h | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index caf22e84a743..d7accc5f8892 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -443,9 +443,7 @@ extern int rcu_my_thread_group_empty(void); }) #define __rcu_assign_pointer(p, v, space) \ ({ \ - if (!__builtin_constant_p(v) || \ - ((v) != NULL)) \ - smp_wmb(); \ + smp_wmb(); \ (p) = (typeof(*v) __force space *)(v); \ }) |