Re: [PATCH] service: fix shifts to operate on 64 bit integers

From: Gaëtan Rivet [mailto:gaetan.rivet@6wind.com]
Sent: Monday, July 31, 2017 5:18 PM
To: Van Haaren, Harry <redacted>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] service: fix shifts to operate on 64 bit integers

Hi Harry,

On Mon, Jul 31, 2017 at 04:58:27PM +0100, Harry van Haaren wrote:

quoted

This commit fixes shifts to an integer (1 << shift) which
is assumed to be a 32-bit integer. In this case, the shift is
variable and expected to be valid for 64-bit integers. Given that
the expectation to work with 64 bits exists, we must ensure that
the (1 << shift) one in that formula is actually a uin64_t.

Simply defining a const uint64_t and using it ensures the compiler
is aware of the intention. The issue would only manifest if there
were greater than 31 services registered.

Fixes: 21698354c832 ("service: introduce service cores concept")

Signed-off-by: Harry van Haaren <redacted>
---
 lib/librte_eal/common/rte_service.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/lib/librte_eal/common/rte_service.c b/lib/librte_eal/common/rte_service.c
index e82b9ad..8c1cffa 100644
--- a/lib/librte_eal/common/rte_service.c
+++ b/lib/librte_eal/common/rte_service.c

@@ -285,8 +285,9 @@ rte_service_unregister(struct rte_service_spec *spec)

 	s->internal_flags &= ~(SERVICE_F_REGISTERED);

+	const uint64_t one = 1;
 	for (i = 0; i < RTE_MAX_LCORE; i++)
-		lcore_states[i].service_mask &= ~(1 << service_id);
+		lcore_states[i].service_mask &= ~(one << service_id);

Why not use UINT64_C(1)?

Mostly because I've never heard of it before :) Thanks for review, still learnin' every day! Sending v2's every other day...