From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sog-mx-2.v43.ch3.sourceforge.com ([172.29.43.192] helo=mx.sourceforge.net) by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.69) (envelope-from ) id 1P9Bwm-0004vv-0F for ltp-list@lists.sourceforge.net; Fri, 22 Oct 2010 07:21:52 +0000 Received: from [222.73.24.84] (helo=song.cn.fujitsu.com) by sog-mx-2.v43.ch3.sourceforge.com with esmtp (Exim 4.69) id 1P9Bwk-0007df-0D for ltp-list@lists.sourceforge.net; Fri, 22 Oct 2010 07:21:51 +0000 Message-ID: <4CC13BB8.7090003@cn.fujitsu.com> Date: Fri, 22 Oct 2010 15:22:32 +0800 From: Li Zefan MIME-Version: 1.0 References: <4C85A88D.10700@cn.fujitsu.com> <1285689961.11429.12.camel@subratamodak.linux.ibm.com> <1286954486.4893.15.camel@subratamodak.linux.ibm.com> <4CB55FE6.6000604@cn.fujitsu.com> <4CB5615C.4070406@cn.fujitsu.com> <4CB59825.7060504@cn.fujitsu.com> <1286995066.4893.17.camel@subratamodak.linux.ibm.com> <4CBBBCB0.8070406@cn.fujitsu.com> <20101021215212.4a982c85@kryten> In-Reply-To: <20101021215212.4a982c85@kryten> Subject: Re: [LTP] [PATCH] powerpc: Fix hcall tracepoint recursion List-Id: Linux Test Project General Discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ltp-list-bounces@lists.sourceforge.net To: Anton Blanchard , subrata@linux.vnet.ibm.com Cc: ltp-list@lists.sourceforge.net, Peter Zijlstra , LKML , Steven Rostedt , Paul Mackerras , Ingo Molnar , linuxppc-dev@lists.ozlabs.org Anton Blanchard wrote: > Hi, > >> This is a dead loop: >> >> trace_hcall_entry() -> trace_clock_global() -> trace_hcall_entry() .. >> >> And this is a PPC specific bug. Hope some ppc guys will fix it? >> Or we kill trace_clock_global() if no one actually uses it.. > > Nasty! How does the patch below look? I had to disable irqs otherwise > we would sometimes drop valid events (if we take an interrupt anywhere > in the region where depth is elevated, then the entire interrupt will > be blocked from calling hcall tracepoints. > Thanks! Subrata, could you test the patch below? > Anton > -- > > Subject: [PATCH] powerpc: Fix hcall tracepoint recursion > > Spinlocks on shared processor partitions use H_YIELD to notify the > hypervisor we are waiting on another virtual CPU. Unfortunately this means > the hcall tracepoints can recurse. > > The patch below adds a percpu depth and checks it on both the entry and > exit hcall tracepoints. > > Signed-off-by: Anton Blanchard > --- > > Index: powerpc.git/arch/powerpc/platforms/pseries/lpar.c > =================================================================== > --- powerpc.git.orig/arch/powerpc/platforms/pseries/lpar.c 2010-10-21 17:32:00.980003644 +1100 > +++ powerpc.git/arch/powerpc/platforms/pseries/lpar.c 2010-10-21 17:34:54.942681273 +1100 > @@ -701,6 +701,13 @@ EXPORT_SYMBOL(arch_free_page); > /* NB: reg/unreg are called while guarded with the tracepoints_mutex */ > extern long hcall_tracepoint_refcount; > > +/* > + * Since the tracing code might execute hcalls we need to guard against > + * recursion. One example of this are spinlocks calling H_YIELD on > + * shared processor partitions. > + */ > +static DEFINE_PER_CPU(unsigned int, hcall_trace_depth); > + > void hcall_tracepoint_regfunc(void) > { > hcall_tracepoint_refcount++; > @@ -713,12 +720,42 @@ void hcall_tracepoint_unregfunc(void) > > void __trace_hcall_entry(unsigned long opcode, unsigned long *args) > { > + unsigned long flags; > + unsigned int *depth; > + > + local_irq_save(flags); > + > + depth = &__get_cpu_var(hcall_trace_depth); > + > + if (*depth) > + goto out; > + > + (*depth)++; > trace_hcall_entry(opcode, args); > + (*depth)--; > + > +out: > + local_irq_restore(flags); > } > > void __trace_hcall_exit(long opcode, unsigned long retval, > unsigned long *retbuf) > { > + unsigned long flags; > + unsigned int *depth; > + > + local_irq_save(flags); > + > + depth = &__get_cpu_var(hcall_trace_depth); > + > + if (*depth) > + goto out; > + > + (*depth)++; > trace_hcall_exit(opcode, retval, retbuf); > + (*depth)--; > + > +out: > + local_irq_restore(flags); > } > #endif > > ------------------------------------------------------------------------------ Nokia and AT&T present the 2010 Calling All Innovators-North America contest Create new apps & games for the Nokia N8 for consumers in U.S. and Canada $10 million total in prizes - $4M cash, 500 devices, nearly $6M in marketing Develop with Nokia Qt SDK, Web Runtime, or Java and Publish to Ovi Store http://p.sf.net/sfu/nokia-dev2dev _______________________________________________ Ltp-list mailing list Ltp-list@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/ltp-list