From ba33034fffc1189d95301bd865f1c799256e72a2 Mon Sep 17 00:00:00 2001 From: Christian Borntraeger Date: Tue, 4 Aug 2015 09:55:48 +0200 Subject: [PATCH] locking, compiler.h: Cast away attributes in the WRITE_ONCE() magic The kernel build bot showed a new warning triggered by commit: 76695af20c01 ("locking, arch: use WRITE_ONCE()/READ_ONCE() in smp_store_release()/smp_load_acquire()") because Sparse does not like WRITE_ONCE() accessing elements from the (sparse) RCU address space: fs/afs/inode.c:448:9: sparse: incorrect type in initializer (different address spaces) fs/afs/inode.c:448:9: expected struct afs_permits *__val fs/afs/inode.c:448:9: got void [noderef] * Solution is to force cast away the sparse attributes for the initializer of the union in WRITE_ONCE(). (And as this now gets too long, also split the macro into multiple lines.) Signed-off-by: Christian Borntraeger Signed-off-by: Peter Zijlstra (Intel) Cc: Andrey Konovalov Cc: Linus Torvalds Cc: Paul McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1438674948-38310-2-git-send-email-borntraeger@de.ibm.com Signed-off-by: Ingo Molnar --- include/linux/compiler.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index e08a6ae7c0a4..c836eb2dc44d 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -252,7 +252,12 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s ({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; }) #define WRITE_ONCE(x, val) \ - ({ union { typeof(x) __val; char __c[1]; } __u = { .__val = (val) }; __write_once_size(&(x), __u.__c, sizeof(x)); __u.__val; }) +({ \ + union { typeof(x) __val; char __c[1]; } __u = \ + { .__val = (__force typeof(x)) (val) }; \ + __write_once_size(&(x), __u.__c, sizeof(x)); \ + __u.__val; \ +}) /** * READ_ONCE_CTRL - Read a value heading a control dependency