From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [Question] Hooks for scheduler tracing (CFS) Date: Thu, 26 Jul 2007 09:35:20 +0200 Message-ID: <20070726073520.GA12206@elte.hu> References: <3efb10970707161246se06ab22i32872cfe6fa4f2f6@mail.gmail.com> <1184615557.2698.3.camel@laptopd505.fenrus.org> <20070726072858.GC13061@in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Arjan van de Ven , linux@bohmer.net, LKML , RT-Users , mathieu.desnoyers@polymtl.ca To: Ankita Garg Return-path: Received: from mx3.mail.elte.hu ([157.181.1.138]:57043 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753826AbXGZHfi (ORCPT ); Thu, 26 Jul 2007 03:35:38 -0400 Content-Disposition: inline In-Reply-To: <20070726072858.GC13061@in.ibm.com> Sender: linux-rt-users-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org * Ankita Garg wrote: > The probe point did get triggered, and soon after that I had the > following in dmesg, leading to system hang... > > BUG: scheduling while atomic: softirq-rcu/3/0x00000004/52, CPU#3 > > Call Trace: > <#DB> [] __schedule_bug+0x4b/0x4f > [] __sched_text_start+0xcc/0xaaa > [] dump_trace+0x248/0x25d > [] print_traces+0x9/0xb > [] show_trace+0x5c/0x64 > [] schedule+0xe4/0x104 > [] rt_spin_lock_slowlock+0xfc/0x19e > [] __rt_spin_lock+0x1f/0x21 > [] rt_spin_lock+0x9/0xb > [] > :stap_c1a10b1292b5f87a563f56d89ddfc765_606:_stp_print_flush+0x5f/0xdf > [] > :stap_c1a10b1292b5f87a563f56d89ddfc765_606:probe_1493+0x1f6/0x257 > [] I'd suggest to not put a probe into a preempt-off section - put it to the beginning and to the end of schedule() to capture context-switches. _stp_print_flush() is in the systemtap-generated module, right? Maybe the problem is resolved by changing that spinlock to use raw_spinlock_t / DEFINE_RAW_SPIN_LOCK. Ingo