[dpdk-dev] [PATCH v5 02/21] eal: list acceptable init priorities

Gaëtan Rivet gaetan.rivet at 6wind.com
Thu Apr 12 23:57:47 CEST 2018


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.rivet at 6wind.com>
> > Acked-by: Neil Horman <nhorman at tuxdriver.com>
> > Acked-by: Shreyansh Jain <shreyansh.jain at 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 b/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
> >  rte_log_init(void)
> >  {
> > diff --git a/lib/librte_eal/common/include/rte_bus.h b/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 b/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.
> 
> Neil
> 

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.

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

-- 
Gaëtan Rivet
6WIND


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