From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp05.au.ibm.com (e23smtp05.au.ibm.com [202.81.31.147]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e23smtp05.au.ibm.com", Issuer "GeoTrust SSL CA" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 5A35A2C0089 for ; Tue, 11 Sep 2012 11:37:59 +1000 (EST) Received: from /spool/local by e23smtp05.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Sep 2012 11:36:49 +1000 Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay04.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q8B1SeP626017934 for ; Tue, 11 Sep 2012 11:28:40 +1000 Received: from d23av01.au.ibm.com (loopback [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q8B1bjGJ007715 for ; Tue, 11 Sep 2012 11:37:46 +1000 Message-ID: <1347327463.8364.8.camel@ThinkPad-T420> Subject: [PATCH powerpc,trace] Avoid suspicious RCU usage reporting for some tracepoints From: Li Zhong To: Benjamin Herrenschmidt Date: Tue, 11 Sep 2012 09:37:43 +0800 In-Reply-To: <1347315255.11820.45.camel@pasglop> References: <1347253133.2725.45.camel@ThinkPad-T420> <1347253812.2385.148.camel@pasglop> <1347285742.10751.6.camel@gandalf.local.home> <1347315255.11820.45.camel@pasglop> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: Anton Blanchard , Paul Mackerras , "Paul E. McKenney" , PowerPC email list , Steven Rostedt List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Thank you all, this is the updated patch for your review: There are a few tracepoints in the interrupt code path, which is before irq_enter(), or after irq_exit(), like trace_irq_entry()/trace_irq_exit() in do_IRQ(), trace_timer_interrupt_entry()/trace_timer_interrupt_exit() in timer_interrupt(). If the interrupt is from idle(), and because tracepoint contains RCU read-side critical section, we could see following suspicious RCU usage reported: [ 145.127743] =============================== [ 145.127747] [ INFO: suspicious RCU usage. ] [ 145.127752] 3.6.0-rc3+ #1 Not tainted [ 145.127755] ------------------------------- [ 145.127759] /root/.workdir/linux/arch/powerpc/include/asm/trace.h:33 suspicious rcu_dereference_check() usage! [ 145.127765] [ 145.127765] other info that might help us debug this: [ 145.127765] [ 145.127771] [ 145.127771] RCU used illegally from idle CPU! [ 145.127771] rcu_scheduler_active = 1, debug_locks = 0 [ 145.127777] RCU used illegally from extended quiescent state! [ 145.127781] no locks held by swapper/0/0. [ 145.127785] [ 145.127785] stack backtrace: [ 145.127789] Call Trace: [ 145.127796] [c00000000108b530] [c000000000013c40] .show_stack +0x70/0x1c0 (unreliable) [ 145.127806] [c00000000108b5e0] [c0000000000f59d8] .lockdep_rcu_suspicious+0x118/0x150 [ 145.127813] [c00000000108b680] [c00000000000fc58] .do_IRQ+0x498/0x500 [ 145.127820] [c00000000108b750] [c000000000003950] hardware_interrupt_common+0x150/0x180 [ 145.127828] --- Exception: 501 at .plpar_hcall_norets+0x84/0xd4 [ 145.127828] LR = .check_and_cede_processor+0x38/0x70 [ 145.127836] [c00000000108bab0] [c0000000000665dc] .shared_cede_loop +0x5c/0x100 [ 145.127844] [c00000000108bb70] [c000000000588ab0] .cpuidle_enter +0x30/0x50 [ 145.127850] [c00000000108bbe0] [c000000000588b0c] .cpuidle_enter_state+0x3c/0xb0 [ 145.127857] [c00000000108bc60] [c000000000589730] .cpuidle_idle_call +0x150/0x6c0 [ 145.127863] [c00000000108bd30] [c000000000058440] .pSeries_idle +0x10/0x40 [ 145.127870] [c00000000108bda0] [c00000000001683c] .cpu_idle +0x18c/0x2d0 [ 145.127876] [c00000000108be60] [c00000000000b434] .rest_init +0x124/0x1b0 [ 145.127884] [c00000000108bef0] [c0000000009d0d28] .start_kernel +0x568/0x588 [ 145.127890] [c00000000108bf90] [c000000000009660] .start_here_common +0x20/0x40 This is because the RCU usage in interrupt context should be used in area marked by rcu_irq_enter()/rcu_irq_exit(), called in irq_enter()/irq_exit() respectively. Move them into the irq_enter()/irq_exit() area to avoid the reporting. Signed-off-by: Li Zhong --- arch/powerpc/kernel/irq.c | 8 ++++---- arch/powerpc/kernel/time.c | 8 ++++---- 2 files changed, 8 insertions(+), 8 deletions(-) diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c index 1f017bb..71413f4 100644 --- a/arch/powerpc/kernel/irq.c +++ b/arch/powerpc/kernel/irq.c @@ -489,10 +489,10 @@ void do_IRQ(struct pt_regs *regs) struct pt_regs *old_regs = set_irq_regs(regs); unsigned int irq; - trace_irq_entry(regs); - irq_enter(); + trace_irq_entry(regs); + check_stack_overflow(); /* @@ -511,10 +511,10 @@ void do_IRQ(struct pt_regs *regs) else __get_cpu_var(irq_stat).spurious_irqs++; + trace_irq_exit(regs); + irq_exit(); set_irq_regs(old_regs); - - trace_irq_exit(regs); } void __init init_IRQ(void) diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index e49e931..bd693a1 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -493,8 +493,6 @@ void timer_interrupt(struct pt_regs * regs) */ may_hard_irq_enable(); - trace_timer_interrupt_entry(regs); - __get_cpu_var(irq_stat).timer_irqs++; #if defined(CONFIG_PPC32) && defined(CONFIG_PMAC) @@ -505,6 +503,8 @@ void timer_interrupt(struct pt_regs * regs) old_regs = set_irq_regs(regs); irq_enter(); + trace_timer_interrupt_entry(regs); + if (test_irq_work_pending()) { clear_irq_work_pending(); irq_work_run(); @@ -529,10 +529,10 @@ void timer_interrupt(struct pt_regs * regs) } #endif + trace_timer_interrupt_exit(regs); + irq_exit(); set_irq_regs(old_regs); - - trace_timer_interrupt_exit(regs); } /* -- 1.7.1