From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754973Ab0EWSQd (ORCPT ); Sun, 23 May 2010 14:16:33 -0400 Received: from casper.infradead.org ([85.118.1.10]:46967 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752718Ab0EWSQb (ORCPT ); Sun, 23 May 2010 14:16:31 -0400 Subject: Re: [PATCH 01/10] perf, trace: Remove IRQ-disable from perf/tracepoint interaction From: Peter Zijlstra To: Paul Mackerras Cc: Ingo Molnar , Arnaldo Carvalho de Melo , Frederic Weisbecker , Steven Rostedt , LKML In-Reply-To: <20100523121159.GB3194@brick.ozlabs.ibm.com> References: <20100521090201.326791353@chello.nl> <20100521090710.419716197@chello.nl> <20100523121159.GB3194@brick.ozlabs.ibm.com> Content-Type: text/plain; charset="UTF-8" Date: Sun, 23 May 2010 20:16:27 +0200 Message-ID: <1274638587.1674.1729.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2010-05-23 at 22:11 +1000, Paul Mackerras wrote: > On Fri, May 21, 2010 at 11:02:02AM +0200, Peter Zijlstra wrote: > > > entry = (struct trace_entry *)raw_data; > > - tracing_generic_entry_update(entry, *irq_flags, pc); > > + tracing_generic_entry_update(entry, regs->flags, pc); > > entry->type = type; > > This is breaking on powerpc -- we don't have a "flags" element in > struct pt_regs. What is it trying to do? Get the interrupt enable > state, as local_irq_save(flags) would provide? Yes, I fouled that up. On x86 perf_arch_fetch_caller_regs() stores pt_regs::flags, which is the same as used in local_save_flags(). So to avoid another local_save_flags() for the ftrace code, I wanted to reuse it, and totally forgot the !x86 side of things. Possibly we could remove the local_save_flags() from the perf_arch_fetch_caller_regs() as I'm not sure we actually use pt_regs::flags (Frederic?) and leave the ftrace thing to use local_save_flags(). Something like: --- arch/x86/kernel/cpu/perf_event.c | 1 - kernel/trace/trace_event_perf.c | 4 +++- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index fd4db0d..856aeeb 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -1717,7 +1717,6 @@ void perf_arch_fetch_caller_regs(struct pt_regs *regs, unsigned long ip, int ski */ regs->bp = rewind_frame_pointer(skip + 1); regs->cs = __KERNEL_CS; - local_save_flags(regs->flags); } unsigned long perf_instruction_pointer(struct pt_regs *regs) diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c index 26b8607..cb6f365 100644 --- a/kernel/trace/trace_event_perf.c +++ b/kernel/trace/trace_event_perf.c @@ -157,6 +157,7 @@ __kprobes void *perf_trace_buf_prepare(int size, unsigned short type, struct pt_regs *regs, int *rctxp) { struct trace_entry *entry; + unsigned long flags; char *raw_data; int pc; @@ -174,7 +175,8 @@ __kprobes void *perf_trace_buf_prepare(int size, unsigned short type, memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64)); entry = (struct trace_entry *)raw_data; - tracing_generic_entry_update(entry, regs->flags, pc); + local_save_flags(flags); + tracing_generic_entry_update(entry, flags, pc); entry->type = type; return raw_data;