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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2013-03-27 09:31:28 -0400
committerSteven Rostedt <rostedt@rostedt.homelinux.com>2013-04-08 12:24:23 -0400
commit395b97a3aeff0b8d949ee3e67bf8c11c5ffd6861 (patch)
tree719c1519cc536a5ec0118b107f0edc90bd312fe6
parent5000c418840b309251c5887f0b56503aae30f84c (diff)
ftrace: Do not call stub functions in control loop
The function tracing control loop used by perf spits out a warning if the called function is not a control function. This is because the control function references a per cpu allocated data structure on struct ftrace_ops that is not allocated for other types of functions. commit 0a016409e42 "ftrace: Optimize the function tracer list loop" Had an optimization done to all function tracing loops to optimize for a single registered ops. Unfortunately, this allows for a slight race when tracing starts or ends, where the stub function might be called after the current registered ops is removed. In this case we get the following dump: root# perf stat -e ftrace:function sleep 1 [ 74.339105] WARNING: at include/linux/ftrace.h:209 ftrace_ops_control_func+0xde/0xf0() [ 74.349522] Hardware name: PRIMERGY RX200 S6 [ 74.357149] Modules linked in: sg igb iTCO_wdt ptp pps_core iTCO_vendor_support i7core_edac dca lpc_ich i2c_i801 coretemp edac_core crc32c_intel mfd_core ghash_clmulni_intel dm_multipath acpi_power_meter pcspk r microcode vhost_net tun macvtap macvlan nfsd kvm_intel kvm auth_rpcgss nfs_acl lockd sunrpc uinput xfs libcrc32c sd_mod crc_t10dif sr_mod cdrom mgag200 i2c_algo_bit drm_kms_helper ttm qla2xxx mptsas ahci drm li bahci scsi_transport_sas mptscsih libata scsi_transport_fc i2c_core mptbase scsi_tgt dm_mirror dm_region_hash dm_log dm_mod [ 74.446233] Pid: 1377, comm: perf Tainted: G W 3.9.0-rc1 #1 [ 74.453458] Call Trace: [ 74.456233] [<ffffffff81062e3f>] warn_slowpath_common+0x7f/0xc0 [ 74.462997] [<ffffffff810fbc60>] ? rcu_note_context_switch+0xa0/0xa0 [ 74.470272] [<ffffffff811041a2>] ? __unregister_ftrace_function+0xa2/0x1a0 [ 74.478117] [<ffffffff81062e9a>] warn_slowpath_null+0x1a/0x20 [ 74.484681] [<ffffffff81102ede>] ftrace_ops_control_func+0xde/0xf0 [ 74.491760] [<ffffffff8162f400>] ftrace_call+0x5/0x2f [ 74.497511] [<ffffffff8162f400>] ? ftrace_call+0x5/0x2f [ 74.503486] [<ffffffff8162f400>] ? ftrace_call+0x5/0x2f [ 74.509500] [<ffffffff810fbc65>] ? synchronize_sched+0x5/0x50 [ 74.516088] [<ffffffff816254d5>] ? _cond_resched+0x5/0x40 [ 74.522268] [<ffffffff810fbc65>] ? synchronize_sched+0x5/0x50 [ 74.528837] [<ffffffff811041a2>] ? __unregister_ftrace_function+0xa2/0x1a0 [ 74.536696] [<ffffffff816254d5>] ? _cond_resched+0x5/0x40 [ 74.542878] [<ffffffff8162402d>] ? mutex_lock+0x1d/0x50 [ 74.548869] [<ffffffff81105c67>] unregister_ftrace_function+0x27/0x50 [ 74.556243] [<ffffffff8111eadf>] perf_ftrace_event_register+0x9f/0x140 [ 74.563709] [<ffffffff816254d5>] ? _cond_resched+0x5/0x40 [ 74.569887] [<ffffffff8162402d>] ? mutex_lock+0x1d/0x50 [ 74.575898] [<ffffffff8111e94e>] perf_trace_destroy+0x2e/0x50 [ 74.582505] [<ffffffff81127ba9>] tp_perf_event_destroy+0x9/0x10 [ 74.589298] [<ffffffff811295d0>] free_event+0x70/0x1a0 [ 74.595208] [<ffffffff8112a579>] perf_event_release_kernel+0x69/0xa0 [ 74.602460] [<ffffffff816254d5>] ? _cond_resched+0x5/0x40 [ 74.608667] [<ffffffff8112a640>] put_event+0x90/0xc0 [ 74.614373] [<ffffffff8112a740>] perf_release+0x10/0x20 [ 74.620367] [<ffffffff811a3044>] __fput+0xf4/0x280 [ 74.625894] [<ffffffff811a31de>] ____fput+0xe/0x10 [ 74.631387] [<ffffffff81083697>] task_work_run+0xa7/0xe0 [ 74.637452] [<ffffffff81014981>] do_notify_resume+0x71/0xb0 [ 74.643843] [<ffffffff8162fa92>] int_signal+0x12/0x17 To fix this a new ftrace_ops flag is added that denotes the ftrace_list_end ftrace_ops stub as just that, a stub. This flag is now checked in the control loop and the function is not called if the flag is set. Thanks to Jovi for not just reporting the bug, but also pointing out where the bug was in the code. Link: http://lkml.kernel.org/r/514A8855.7090402@redhat.com Link: http://lkml.kernel.org/r/1364377499-1900-15-git-send-email-jovi.zhangwei@huawei.com Tested-by: WANG Chao <chaowang@redhat.com> Reported-by: WANG Chao <chaowang@redhat.com> Reported-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
-rw-r--r--include/linux/ftrace.h2
-rw-r--r--kernel/trace/ftrace.c5
2 files changed, 5 insertions, 2 deletions
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index e5ca8ef50e9b..167abf907802 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -89,6 +89,7 @@ typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip,
89 * that the call back has its own recursion protection. If it does 89 * that the call back has its own recursion protection. If it does
90 * not set this, then the ftrace infrastructure will add recursion 90 * not set this, then the ftrace infrastructure will add recursion
91 * protection for the caller. 91 * protection for the caller.
92 * STUB - The ftrace_ops is just a place holder.
92 */ 93 */
93enum { 94enum {
94 FTRACE_OPS_FL_ENABLED = 1 << 0, 95 FTRACE_OPS_FL_ENABLED = 1 << 0,
@@ -98,6 +99,7 @@ enum {
98 FTRACE_OPS_FL_SAVE_REGS = 1 << 4, 99 FTRACE_OPS_FL_SAVE_REGS = 1 << 4,
99 FTRACE_OPS_FL_SAVE_REGS_IF_SUPPORTED = 1 << 5, 100 FTRACE_OPS_FL_SAVE_REGS_IF_SUPPORTED = 1 << 5,
100 FTRACE_OPS_FL_RECURSION_SAFE = 1 << 6, 101 FTRACE_OPS_FL_RECURSION_SAFE = 1 << 6,
102 FTRACE_OPS_FL_STUB = 1 << 7,
101}; 103};
102 104
103struct ftrace_ops { 105struct ftrace_ops {
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index cc4943c7ce6d..7e897106b7e0 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -66,7 +66,7 @@
66 66
67static struct ftrace_ops ftrace_list_end __read_mostly = { 67static struct ftrace_ops ftrace_list_end __read_mostly = {
68 .func = ftrace_stub, 68 .func = ftrace_stub,
69 .flags = FTRACE_OPS_FL_RECURSION_SAFE, 69 .flags = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_STUB,
70}; 70};
71 71
72/* ftrace_enabled is a method to turn ftrace on or off */ 72/* ftrace_enabled is a method to turn ftrace on or off */
@@ -4131,7 +4131,8 @@ ftrace_ops_control_func(unsigned long ip, unsigned long parent_ip,
4131 preempt_disable_notrace(); 4131 preempt_disable_notrace();
4132 trace_recursion_set(TRACE_CONTROL_BIT); 4132 trace_recursion_set(TRACE_CONTROL_BIT);
4133 do_for_each_ftrace_op(op, ftrace_control_list) { 4133 do_for_each_ftrace_op(op, ftrace_control_list) {
4134 if (!ftrace_function_local_disabled(op) && 4134 if (!(op->flags & FTRACE_OPS_FL_STUB) &&
4135 !ftrace_function_local_disabled(op) &&
4135 ftrace_ops_test(op, ip)) 4136 ftrace_ops_test(op, ip))
4136 op->func(ip, parent_ip, op, regs); 4137 op->func(ip, parent_ip, op, regs);
4137 } while_for_each_ftrace_op(op); 4138 } while_for_each_ftrace_op(op);