From 3bf832ce1fe6988148d392599f34ca0c6a34427d Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 19 Mar 2009 14:47:33 +0100 Subject: [PATCH] tracing/ring-buffer: fix non cpu hotplug case Impact: fix warning with irqsoff tracer The ring buffer allocates its buffers on pre-smp time (early_initcall). It means that, at first, only the boot cpu buffer is allocated and the ring-buffer cpumask only has the boot cpu set (cpu_online_mask). Later, the secondary cpu will show up and the ring-buffer will be notified about this event: the appropriate buffer will be allocated and the cpumask will be updated. Unfortunately, if !CONFIG_CPU_HOTPLUG, the ring-buffer will not be notified about the secondary cpus, meaning that the cpumask will have only the cpu boot set, and only one cpu buffer allocated. We fix that by using cpu_possible_mask if !CONFIG_CPU_HOTPLUG. This patch fixes the following warning with irqsoff tracer running: [ 169.317794] WARNING: at kernel/trace/trace.c:466 update_max_tr_single+0xcc/0xf3() [ 169.318002] Hardware name: AMILO Li 2727 [ 169.318002] Modules linked in: [ 169.318002] Pid: 5624, comm: bash Not tainted 2.6.29-rc8-tip-02636-g6aafa6c #11 [ 169.318002] Call Trace: [ 169.318002] [] warn_slowpath+0xea/0x13d [ 169.318002] [] ? ftrace_call+0x5/0x2b [ 169.318002] [] ? ftrace_call+0x5/0x2b [ 169.318002] [] ? ftrace_call+0x0/0x2b [ 169.318002] [] ? ftrace_modify_code+0xa9/0x108 [ 169.318002] [] ? trace_hardirqs_off+0x25/0x27 [ 169.318002] [] ? _spin_unlock_irqrestore+0x1f/0x2d [ 169.318002] [] ? ring_buffer_reset_cpu+0xf6/0xfb [ 169.318002] [] ? ring_buffer_reset+0x36/0x48 [ 169.318002] [] update_max_tr_single+0xcc/0xf3 [ 169.318002] [] ? sysret_check+0x22/0x5d [ 169.318002] [] stop_critical_timing+0x142/0x204 [ 169.318002] [] trace_hardirqs_on_caller+0x23/0x25 [ 169.318002] [] trace_hardirqs_on_thunk+0x3a/0x3c [ 169.318002] [] ? sysret_check+0x22/0x5d [ 169.318002] ---[ end trace db76cbf775a750cf ]--- Because this tracer may try to swap two cpu ring buffers for an unregistered cpu on the ring buffer. This patch might also fix a fair loss of traces due to unallocated buffers for secondary cpus. Reported-by: Ingo Molnar Signed-off-by: Frederic Weisbecker Acked-b: Steven Rostedt LKML-Reference: <1237470453-5427-1-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar --- kernel/trace/ring_buffer.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index bbf51922a8ca..384ca5d9d729 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -577,8 +577,17 @@ struct ring_buffer *ring_buffer_alloc(unsigned long size, unsigned flags) if (buffer->pages == 1) buffer->pages++; + /* + * In case of non-hotplug cpu, if the ring-buffer is allocated + * in early initcall, it will not be notified of secondary cpus. + * In that off case, we need to allocate for all possible cpus. + */ +#ifdef CONFIG_HOTPLUG_CPU get_online_cpus(); cpumask_copy(buffer->cpumask, cpu_online_mask); +#else + cpumask_copy(buffer->cpumask, cpu_possible_mask); +#endif buffer->cpus = nr_cpu_ids; bsize = sizeof(void *) * nr_cpu_ids; -- 2.20.1