From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp08.au.ibm.com (e23smtp08.au.ibm.com [202.81.31.141]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e23smtp08.au.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id 29B03B7D1D for ; Wed, 26 May 2010 16:51:40 +1000 (EST) Received: from d23relay03.au.ibm.com (d23relay03.au.ibm.com [202.81.31.245]) by e23smtp08.au.ibm.com (8.14.3/8.13.1) with ESMTP id o4Q6paMp019999 for ; Wed, 26 May 2010 16:51:36 +1000 Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o4Q6pbju483338 for ; Wed, 26 May 2010 16:51:37 +1000 Received: from d23av01.au.ibm.com (loopback [127.0.0.1]) by d23av01.au.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id o4Q6pZxr021207 for ; Wed, 26 May 2010 16:51:37 +1000 Date: Wed, 26 May 2010 12:21:29 +0530 From: "K.Prasad" To: Millton Miller Subject: Re: [Patch 1/4] Allow arch-specific cleanup before breakpoint unregistration Message-ID: <20100526065129.GA3746@in.ibm.com> References: <20100525083055.342788418@linux.vnet.ibm.com> <20100525091356.GB29003@in.ibm.com> <1274787559_8162@mail4.comsite.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1274787559_8162@mail4.comsite.net> Cc: Michael Neuling , Benjamin Herrenschmidt , shaggy@linux.vnet.ibm.com, Frederic Weisbecker , Linux Kernel Mailing List , David Gibson , "linuxppc-dev@ozlabs.org" , Alan Stern , Paul Mackerras , Andrew Morton , Roland McGrath Reply-To: prasad@linux.vnet.ibm.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, May 25, 2010 at 06:39:19AM -0500, Millton Miller wrote: > On Tue, 25 May 2010 at 14:43:56 +0530, K.Prasad wrote: > > Certain architectures (such as PowerPC Book III S) have a need to cleanup > > data-structures before the breakpoint is unregistered. This patch introduces > > an arch-specific hook in release_bp_slot() along with a weak definition in > > the form of a stub funciton. > > > > Signed-off-by: K.Prasad > > --- > > kernel/hw_breakpoint.c | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > My understanding is weak function definitions must appear in a different C > file than their call sites to work on some toolchains. > Atleast, there are quite a few precedents inside the Linux kernel for __weak functions being invoked from the file in which they are defined (arch_hwblk_init, arch_enable_nonboot_cpus_begin and hw_perf_disable to name a few). Moreover the online GCC docs haven't any such constraints mentioned. > Andrew, can you confirm the above statement? > > > Index: linux-2.6.ppc64_test/kernel/hw_breakpoint.c > > =================================================================== > > --- linux-2.6.ppc64_test.orig/kernel/hw_breakpoint.c > > +++ linux-2.6.ppc64_test/kernel/hw_breakpoint.c > > @@ -242,6 +242,17 @@ toggle_bp_slot(struct perf_event *bp, bo > > } > > > > /* > > + * Function to perform processor-specific cleanup during unregistration > > + */ > > +__weak void arch_unregister_hw_breakpoint(struct perf_event *bp) > > +{ > > + /* > > + * A weak stub function here for those archs that don't define > > + * it inside arch/.../kernel/hw_breakpoint.c > > + */ > > +} > > + > > +/* > > * Contraints to check before allowing this new breakpoint counter: > > * > > * == Non-pinned counter == (Considered as pinned for now) > > @@ -339,6 +350,7 @@ void release_bp_slot(struct perf_event * > > { > > mutex_lock(&nr_bp_mutex); > > > > + arch_unregister_hw_breakpoint(bp); > > __release_bp_slot(bp); > > > > mutex_unlock(&nr_bp_mutex); > > > > > Since the weak version is empty, should it just be delcared (in > a header, put the comment there) and not defined? > The initial thinking behind defining it in the .c file was, for one, the function need not be moved (from .h to .c) when other architectures have a need to populate them. Secondly, given that powerpc (which has a 'strong' definition for arch_unregister_hw_breakpoint()) includes the header file (in which this can be moved to) I wasn't sure about possible conflicts. > milton > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev Thanks, K.Prasad