From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756083Ab1IGGaM (ORCPT ); Wed, 7 Sep 2011 02:30:12 -0400 Received: from e7.ny.us.ibm.com ([32.97.182.137]:40006 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755658Ab1IGGUt (ORCPT ); Wed, 7 Sep 2011 02:20:49 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, patches@linaro.org, "Paul E. McKenney" , anton@samba.org, benh@kernel.crashing.org, paulus@samba.org Subject: [PATCH tip/core/rcu 55/55] powerpc: Work around tracing from dyntick-idle mode Date: Tue, 6 Sep 2011 11:00:49 -0700 Message-Id: <1315332049-2604-55-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.3.2 In-Reply-To: <20110906180015.GA2560@linux.vnet.ibm.com> References: <20110906180015.GA2560@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org PowerPC LPAR's __trace_hcall_exit() can invoke event tracing at a point where RCU has been told that the CPU is in dyntick-idle mode. Because event tracing uses RCU, this can result in failures. A correct fix would arrange for RCU to be told about dyntick-idle mode after tracing had completed, however, this will require some care because it appears that __trace_hcall_exit() can also be called from non-dyntick-idle mode. Signed-off-by: Paul E. McKenney Cc: anton@samba.org Cc: benh@kernel.crashing.org Cc: paulus@samba.org --- arch/powerpc/platforms/pseries/lpar.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-) diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index 39e6e0a..668f300 100644 --- a/arch/powerpc/platforms/pseries/lpar.c +++ b/arch/powerpc/platforms/pseries/lpar.c @@ -715,12 +715,14 @@ EXPORT_SYMBOL(arch_free_page); /* NB: reg/unreg are called while guarded with the tracepoints_mutex */ extern long hcall_tracepoint_refcount; +#if 0 /* work around buggy use of RCU from dyntick-idle mode */ /* * 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); +#endif /* #if 0 work around buggy use of RCU from dyntick-idle mode */ void hcall_tracepoint_regfunc(void) { @@ -734,6 +736,7 @@ void hcall_tracepoint_unregfunc(void) void __trace_hcall_entry(unsigned long opcode, unsigned long *args) { +#if 0 /* work around buggy use of RCU from dyntick-idle mode */ unsigned long flags; unsigned int *depth; @@ -750,11 +753,13 @@ void __trace_hcall_entry(unsigned long opcode, unsigned long *args) out: local_irq_restore(flags); +#endif /* #if 0 work around buggy use of RCU from dyntick-idle mode */ } void __trace_hcall_exit(long opcode, unsigned long retval, unsigned long *retbuf) { +#if 0 /* work around buggy use of RCU from dyntick-idle mode */ unsigned long flags; unsigned int *depth; @@ -771,6 +776,7 @@ void __trace_hcall_exit(long opcode, unsigned long retval, out: local_irq_restore(flags); +#endif /* #if 0 work around buggy use of RCU from dyntick-idle mode */ } #endif -- 1.7.3.2