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Subject[patch] ipvs: force read of atomic_t in while loop
From: Heiko Carstens <heiko.carstens@de.ibm.com>

For architectures that don't have a volatile atomic_ts constructs like
while (atomic_read(&something)); might result in endless loops since a
barrier() is missing which forces the compiler to generate code that
actually reads memory contents.
Fix this in ipvs by using the IP_VS_WAIT_WHILE macro which resolves to
while (expr) { cpu_relax(); }
(why isn't this open coded btw?)

Cc: Wensong Zhang <wensong@linux-vs.org>
Cc: Simon Horman <horms@verge.net.au>
Cc: David Miller <davem@davemloft.net>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
---

Just saw this while grepping for atomic_reads in a while loops.
Maybe we should re-add the volatile to atomic_t. Not sure.

net/ipv4/ipvs/ip_vs_ctl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/net/ipv4/ipvs/ip_vs_ctl.c
===================================================================
--- linux-2.6.orig/net/ipv4/ipvs/ip_vs_ctl.c
+++ linux-2.6/net/ipv4/ipvs/ip_vs_ctl.c
@@ -909,7 +909,7 @@ ip_vs_edit_dest(struct ip_vs_service *sv
write_lock_bh(&__ip_vs_svc_lock);

/* Wait until all other svc users go away */
- while (atomic_read(&svc->usecnt) > 1) {};
+ IP_VS_WAIT_WHILE(atomic_read(&svc->usecnt) > 1);

/* call the update_service, because server weight may be changed */
svc->scheduler->update_service(svc);
-
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