[dpdk-dev] [PATCH v3 8/9] mem: fix statement having no effect

[Anatoly Burakov <anatoly.burakov@intel.com>]

Coverity reports these lines as having no effect. Technically, we do
want for those lines to have no effect, however they would've likely
been optimized out. Add volatile qualifiers to ensure the code has
effects.

Coverity issue: 272608

Fixes: 582bed1e1d1d ("mem: support mapping hugepages at runtime")
Cc: anatoly.burakov@intel.com

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
 lib/librte_eal/linuxapp/eal/eal_memalloc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/librte_eal/linuxapp/eal/eal_memalloc.c b/lib/librte_eal/linuxapp/eal/eal_memalloc.c
index 6a75e5b..655c69e 100644
--- a/lib/librte_eal/linuxapp/eal/eal_memalloc.c
+++ b/lib/librte_eal/linuxapp/eal/eal_memalloc.c
@@ -503,7 +503,12 @@ alloc_seg(struct rte_memseg *ms, void *addr, int socket_id,
 			(unsigned int)(alloc_sz >> 20));
 		goto mapped;
 	}
-	*(int *)addr = *(int *)addr;
+	/* we need to trigger a write to the page to enforce page fault and
+	 * ensure that page is accessible to us, but we can't overwrite value
+	 * that is already there, so read the old value, and write itback.
+	 * kernel populates the page with zeroes initially.
+	 */
+	*(volatile int *)addr = *(volatile int *)addr;
 
 	ms->addr = addr;
 	ms->hugepage_sz = alloc_sz;
-- 
2.7.4