From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?iso-8859-1?Q?Ga=EBtan?= Rivet Subject: Re: [PATCH v5 02/21] eal: list acceptable init priorities Date: Fri, 13 Apr 2018 14:55:11 +0200 Message-ID: <20180413125511.p2xhkc2355lohwqs@bidouze.vm.6wind.com> References: <3c46c7947bec6462e07a6c33e39f680c8d9e688b.1523404469.git.gaetan.rivet@6wind.com> <20180412112826.GA8105@hmswarspite.think-freely.org> <20180412215747.f5ga5dh6rfoqx46l@bidouze.vm.6wind.com> <20180413114246.GB1699@hmswarspite.think-freely.org> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Cc: Neil Horman , dev@dpdk.org To: Shreyansh Jain Return-path: Received: from mail-wr0-f196.google.com (mail-wr0-f196.google.com [209.85.128.196]) by dpdk.org (Postfix) with ESMTP id A6E711BDA2 for ; Fri, 13 Apr 2018 14:55:26 +0200 (CEST) Received: by mail-wr0-f196.google.com with SMTP id v60so4290977wrc.7 for ; Fri, 13 Apr 2018 05:55:26 -0700 (PDT) Content-Disposition: inline In-Reply-To: List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Hi Shreyansh, On Fri, Apr 13, 2018 at 06:22:43PM +0530, Shreyansh Jain wrote: > 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 > > > > > Acked-by: Neil Horman > > > > > Acked-by: Shreyansh Jain > > > > > --- > > > > > 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. > > > > > 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; > --->8--- > > 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. This is interesting, thanks for looking up the GCC code. Ok, unless someone has a strong reason not to, I will add RTE_PRIORITY_LAST. Not really convinced about it but not opposed enough either :) . Regards, -- Gaëtan Rivet 6WIND