On Friday 13 April 2018 05:12 PM, Neil Horman wrote:
On Thu, Apr 12, 2018 at 11:57:47PM +0200, Gaëtan Rivet wrote:
Hello Neil,

On Thu, Apr 12, 2018 at 07:28:26AM -0400, Neil Horman wrote:
On Wed, Apr 11, 2018 at 02:04:03AM +0200, Gaetan Rivet wrote:
Build a central list to quickly see each used priorities for
constructors, allowing to verify that they are both above 100 and in the
proper order.

Signed-off-by: Gaetan Rivet <gaetan.ri...@6wind.com>
Acked-by: Neil Horman <nhor...@tuxdriver.com>
Acked-by: Shreyansh Jain <shreyansh.j...@nxp.com>
  lib/librte_eal/common/eal_common_log.c     | 2 +-
  lib/librte_eal/common/include/rte_bus.h    | 2 +-
  lib/librte_eal/common/include/rte_common.h | 8 +++++++-
  3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/lib/librte_eal/common/eal_common_log.c 
index a27192620..36b9d6e08 100644
--- a/lib/librte_eal/common/eal_common_log.c
+++ b/lib/librte_eal/common/eal_common_log.c
@@ -260,7 +260,7 @@ static const struct logtype logtype_strings[] = {
/* Logging should be first initializer (before drivers and bus) */
-RTE_INIT_PRIO(rte_log_init, 101);
+RTE_INIT_PRIO(rte_log_init, LOG);
  static void
diff --git a/lib/librte_eal/common/include/rte_bus.h 
index 6fb08341a..eb9eded4e 100644
--- a/lib/librte_eal/common/include/rte_bus.h
+++ b/lib/librte_eal/common/include/rte_bus.h
@@ -325,7 +325,7 @@ enum rte_iova_mode rte_bus_get_iommu_class(void);
   * The constructor has higher priority than PMD constructors.
  #define RTE_REGISTER_BUS(nm, bus) \
-RTE_INIT_PRIO(businitfn_ ##nm, 110); \
+RTE_INIT_PRIO(businitfn_ ##nm, BUS); \
  static void businitfn_ ##nm(void) \
        (bus).name = RTE_STR(nm);\
diff --git a/lib/librte_eal/common/include/rte_common.h 
index 6c5bc5a76..8f04518f7 100644
--- a/lib/librte_eal/common/include/rte_common.h
+++ b/lib/librte_eal/common/include/rte_common.h
@@ -81,6 +81,12 @@ typedef uint16_t unaligned_uint16_t;
  #define RTE_SET_USED(x) (void)(x)
+#define RTE_PRIORITY_LOG 101
+#define RTE_PRIORITY_BUS 110
+#define RTE_PRIO(prio) \
+       RTE_PRIORITY_ ## prio
   * Run function before main() with low priority.
@@ -102,7 +108,7 @@ static void __attribute__((constructor, used)) func(void)
   *   Lowest number is the first to run.
  #define RTE_INIT_PRIO(func, prio) \
-static void __attribute__((constructor(prio), used)) func(void)
+static void __attribute__((constructor(RTE_PRIO(prio)), used)) func(void)
It just occured to me, that perhaps you should add a RTE_PRORITY_LAST priority,
and redefine RTE_INIT to RTE_INIT_PRIO(func, RTE_PRIORITY_LAST) for clarity.  I
presume that constructors with no explicit priority run last, but the gcc
manual doesn't explicitly say that.  It would be a heck of a bug to track down
if somehow unprioritized constructors ran early.


While certainly poorly documented, the behavior is well-defined. I don't see
a situation where the bug you describe could arise.

Adding RTE_PRIORITY_LAST is pretty harmless, but I'm not sure it's
justified to add it. If you still think it is useful, I will do it.

It was more just a way to unify the macros is all, probably not important.

I'd be curious to hear if anyone has had issues of this kind.

I've not had any, but I was suprised to see that the gcc manual didn't
explicitly call out the implied priority of unprioritized constructors

I (tried to) looked into the gcc code base. It seems that when priority is not defined, DEFAULT_INIT_PRIORITY 65536, is used.

--->8--- gcc/collect2.c ---
  /* Extract init_p number from ctor/dtor name.  */
  pri = atoi (name + pos);
  return pri ? pri : DEFAULT_INIT_PRIORITY;

Though, I couldn't find any documentation for this fact - and, I can never be confident about gcc code.

I found one of the ARM compiler (clang) does has a policy for using non-specified priority as lower than specified priority. [1]

[1] https://developer.arm.com/docs/dui0774/latest/compiler-specific-function-variable-and-type-attributes/__attribute__constructorpriority-function-attribute

A specified value for RTE_PRIORITY_LAST is not a bad option - it would help in keeping the priorities bound without relying on the unknown of priority for unspecified constructors.


Gaëtan Rivet

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