[PATCH v2] eal: avoid issues in macro expansion of alignment

[Stephen Hemminger]

RTE_ALIGN_MUL_NEAR is a macro so the cycle argument could
get evaluated twice causing some potential skew.  Fix by
computing value once.

Suggested by patch to fix side effects.

Fixes: 5cbd14b3e5f9 ("eal: roundup TSC frequency when estimating")
Cc: pbhagavatula at marvell.com
Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
---
v2 - fix spelling error in commit message

 lib/eal/common/eal_common_timer.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/lib/eal/common/eal_common_timer.c b/lib/eal/common/eal_common_timer.c
index 5686a5102b66..05614b0503cf 100644
--- a/lib/eal/common/eal_common_timer.c
+++ b/lib/eal/common/eal_common_timer.c
@@ -42,10 +42,14 @@ estimate_tsc_freq(void)
 	RTE_LOG(WARNING, EAL, "WARNING: TSC frequency estimated roughly"
 		" - clock timings may be less accurate.\n");
 	/* assume that the rte_delay_us_sleep() will sleep for 1 second */
-	uint64_t start = rte_rdtsc();
+	uint64_t start, elapsed;
+
+	start = rte_rdtsc();
 	rte_delay_us_sleep(US_PER_S);
+	elapsed = rte_rdtsc() - start;
+
 	/* Round up to 10Mhz. 1E7 ~ 10Mhz */
-	return RTE_ALIGN_MUL_NEAR(rte_rdtsc() - start, CYC_PER_10MHZ);
+	return RTE_ALIGN_MUL_NEAR(elapsed, CYC_PER_10MHZ);
 }
 
 void
-- 
2.39.2