diff mbox

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

Message ID bd203d4166eec8f9473e336a58d3296f8eb2a470.1524650130.git.anatoly.burakov@intel.com (mailing list archive)
State Superseded, archived
Delegated to: Thomas Monjalon
Headers

Checks

Context Check Description
ci/checkpatch success coding style OK
ci/Intel-compilation fail apply patch file failure

Commit Message

Burakov, Anatoly April 25, 2018, 9:56 a.m. UTC 
  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(-)

Comments

Bruce Richardson April 27, 2018, 3:39 p.m. UTC | #1 
On Wed, Apr 25, 2018 at 10:56:46AM +0100, Anatoly Burakov wrote:
> 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>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
diff mbox

Patch

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;