[PATCH] random: clarify PRNG MT safety guarantees

["Mattias Rönnblom" <mattias.ronnblom@ericsson.com>]

Clarify MT safety guarantees for unregistered non-EAL threads calling
PRNG functions in rte_random.h.

Clarify that rte_srand() is not MT safe in regards to calls to
rte_rand_max() and rte_drand().

Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
Suggested-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/eal/include/rte_random.h | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/lib/eal/include/rte_random.h b/lib/eal/include/rte_random.h
index 2edf5d210b..c12eb07ea8 100644
--- a/lib/eal/include/rte_random.h
+++ b/lib/eal/include/rte_random.h
@@ -27,8 +27,8 @@ extern "C" {
  * value.
  *
  * This function is not multi-thread safe in regards to other
- * rte_srand() calls, nor is it in relation to concurrent rte_rand()
- * calls.
+ * rte_srand() calls, nor is it in relation to concurrent rte_rand(),
+ * rte_rand_max() or rte_drand() calls.
  *
  * @param seedval
  *   The value of the seed.
@@ -41,8 +41,9 @@ rte_srand(uint64_t seedval);
  *
  * The generator is not cryptographically secure.
  *
- * If called from EAL threads or registered non-EAL threads, this function
- * is thread-safe.
+ * rte_rand(), rte_rand_max() and rte_drand() are multi-thread safe,
+ * with the exception that they may not be called by multiple
+ * _unregistered_ non-EAL threads in parallel.
  *
  * @return
  *   A pseudo-random value between 0 and (1<<64)-1.
@@ -56,8 +57,9 @@ rte_rand(void);
  * This function returns an uniformly distributed (unbiased) random
  * number less than a user-specified maximum value.
  *
- * If called from EAL threads or registered non-EAL threads, this function
- * is thread-safe.
+ * rte_rand(), rte_rand_max() and rte_drand() are multi-thread safe,
+ * with the exception that they may not be called by multiple
+ * _unregistered_ non-EAL threads in parallel.
  *
  * @param upper_bound
  *   The upper bound of the generated number.
@@ -78,8 +80,9 @@ rte_rand_max(uint64_t upper_bound);
  *
  * The generator is not cryptographically secure.
  *
- * If called from EAL threads or registered non-EAL threads, this function
- * is thread-safe.
+ * rte_rand(), rte_rand_max() and rte_drand() are multi-thread safe,
+ * with the exception that they may not be called by multiple
+ * _unregistered_ non-EAL threads in parallel.
  *
  * @return
  *   A pseudo-random value between 0 and 1.0.
-- 
2.34.1