From f27107fa20ad531ace5fd580473ff8dd0c6b9ca9 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Tue, 7 Aug 2018 17:03:12 -0400 Subject: tracing/irqsoff: Handle preempt_count for different configs I was hitting the following warning: WARNING: CPU: 0 PID: 1 at kernel/trace/trace_irqsoff.c:631 tracer_hardirqs_off+0x15/0x2a Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.18.0-rc6-test+ #13 Hardware name: MSI MS-7823/CSM-H87M-G43 (MS-7823), BIOS V1.6 02/22/2014 EIP: tracer_hardirqs_off+0x15/0x2a Code: ff 85 c0 74 0e 8b 45 00 8b 50 04 8b 45 04 e8 35 ff ff ff 5d c3 55 64 a1 cc 37 51 c1 a9 ff ff ff 7f 89 e5 53 89 d3 89 ca 75 02 <0f> 0b e8 90 fc ff ff 85 c0 74 07 89 d8 e8 0c ff ff ff 5b 5d c3 55 EAX: 80000000 EBX: c04337f0 ECX: c04338e3 EDX: c04338e3 ESI: c04337f0 EDI: c04338e3 EBP: f2aa1d68 ESP: f2aa1d64 DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00210046 CR0: 80050033 CR2: 00000000 CR3: 01668000 CR4: 001406f0 Call Trace: trace_irq_disable_rcuidle+0x63/0x6c trace_hardirqs_off+0x26/0x30 default_send_IPI_mask_allbutself_logical+0x31/0x93 default_send_IPI_allbutself+0x37/0x48 native_send_call_func_ipi+0x4d/0x6a smp_call_function_many+0x165/0x19d ? add_nops+0x34/0x34 ? trace_hardirqs_on_caller+0x2d/0x2d ? add_nops+0x34/0x34 smp_call_function+0x1f/0x23 on_each_cpu+0x15/0x43 ? trace_hardirqs_on_caller+0x2d/0x2d ? trace_hardirqs_on_caller+0x2d/0x2d ? trace_irq_disable_rcuidle+0x1/0x6c text_poke_bp+0xa0/0xc2 ? trace_hardirqs_on_caller+0x2d/0x2d arch_jump_label_transform+0xa7/0xcb ? trace_irq_disable_rcuidle+0x5/0x6c __jump_label_update+0x3e/0x6d jump_label_update+0x7d/0x81 static_key_slow_inc_cpuslocked+0x58/0x6d static_key_slow_inc+0x19/0x20 tracepoint_probe_register_prio+0x19e/0x1d1 ? start_critical_timings+0x1c/0x1c tracepoint_probe_register+0xf/0x11 irqsoff_tracer_init+0x21/0xf2 tracer_init+0x16/0x1a trace_selftest_startup_irqsoff+0x25/0xc4 run_tracer_selftest+0xca/0x131 register_tracer+0xd5/0x172 ? trace_event_define_fields_preemptirq_template+0x45/0x45 init_irqsoff_tracer+0xd/0x11 do_one_initcall+0xab/0x1e8 ? rcu_read_lock_sched_held+0x3d/0x44 ? trace_initcall_level+0x52/0x86 kernel_init_freeable+0x195/0x21a ? rest_init+0xb4/0xb4 kernel_init+0xd/0xe4 ret_from_fork+0x2e/0x38 It is due to running a CONFIG_PREEMPT_VOLUNTARY kernel, which would trigger this warning every time: WARN_ON_ONCE(preempt_count()); Because on CONFIG_PREEMPT_VOLUNTARY, preempt_count() is always zero. This warning is to make sure preempt_count is set because tracer_hardirqs_on() does a preempt_enable_notrace() to make the preempt_trace() work properly, as being called by a trace event, the trace event code disables preemption, and the tracer wants to know what the preemption was before it was called. Instead of enabling preemption like this, just record the preempt_count, subtract PREEMPT_DISABLE_OFFSET from it (which is zero with !CONFIG_PREEMPT set), and pass that value to the necessary functions, which should use the passed in parameter instead of calling preempt_count() directly. Fixes: da5b3ebb45277 ("tracing: irqsoff: Account for additional preempt_disable") Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_irqsoff.c | 66 +++++++++++++++++++++++++------------------- 1 file changed, 37 insertions(+), 29 deletions(-) (limited to 'kernel') diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c index ffbf1505d5bc..4af990e9c594 100644 --- a/kernel/trace/trace_irqsoff.c +++ b/kernel/trace/trace_irqsoff.c @@ -40,12 +40,12 @@ static int start_irqsoff_tracer(struct trace_array *tr, int graph); #ifdef CONFIG_PREEMPT_TRACER static inline int -preempt_trace(void) +preempt_trace(int pc) { - return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count()); + return ((trace_type & TRACER_PREEMPT_OFF) && pc); } #else -# define preempt_trace() (0) +# define preempt_trace(pc) (0) #endif #ifdef CONFIG_IRQSOFF_TRACER @@ -366,7 +366,7 @@ out: } static inline void -start_critical_timing(unsigned long ip, unsigned long parent_ip) +start_critical_timing(unsigned long ip, unsigned long parent_ip, int pc) { int cpu; struct trace_array *tr = irqsoff_trace; @@ -394,7 +394,7 @@ start_critical_timing(unsigned long ip, unsigned long parent_ip) local_save_flags(flags); - __trace_function(tr, ip, parent_ip, flags, preempt_count()); + __trace_function(tr, ip, parent_ip, flags, pc); per_cpu(tracing_cpu, cpu) = 1; @@ -402,7 +402,7 @@ start_critical_timing(unsigned long ip, unsigned long parent_ip) } static inline void -stop_critical_timing(unsigned long ip, unsigned long parent_ip) +stop_critical_timing(unsigned long ip, unsigned long parent_ip, int pc) { int cpu; struct trace_array *tr = irqsoff_trace; @@ -428,7 +428,7 @@ stop_critical_timing(unsigned long ip, unsigned long parent_ip) atomic_inc(&data->disabled); local_save_flags(flags); - __trace_function(tr, ip, parent_ip, flags, preempt_count()); + __trace_function(tr, ip, parent_ip, flags, pc); check_critical_timing(tr, data, parent_ip ? : ip, cpu); data->critical_start = 0; atomic_dec(&data->disabled); @@ -437,15 +437,19 @@ stop_critical_timing(unsigned long ip, unsigned long parent_ip) /* start and stop critical timings used to for stoppage (in idle) */ void start_critical_timings(void) { - if (preempt_trace() || irq_trace()) - start_critical_timing(CALLER_ADDR0, CALLER_ADDR1); + int pc = preempt_count(); + + if (preempt_trace(pc) || irq_trace()) + start_critical_timing(CALLER_ADDR0, CALLER_ADDR1, pc); } EXPORT_SYMBOL_GPL(start_critical_timings); void stop_critical_timings(void) { - if (preempt_trace() || irq_trace()) - stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1); + int pc = preempt_count(); + + if (preempt_trace(pc) || irq_trace()) + stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1, pc); } EXPORT_SYMBOL_GPL(stop_critical_timings); @@ -603,40 +607,40 @@ static void irqsoff_tracer_stop(struct trace_array *tr) */ static void tracer_hardirqs_on(void *none, unsigned long a0, unsigned long a1) { + unsigned int pc = preempt_count(); + /* * Tracepoint probes are expected to be called with preempt disabled, * We don't care about being called with preempt disabled but we need * to know in the future if that changes so we can remove the next * preempt_enable. */ - WARN_ON_ONCE(!preempt_count()); - - /* Tracepoint probes disable preemption atleast once, account for that */ - preempt_enable_notrace(); + WARN_ON_ONCE(pc < PREEMPT_DISABLE_OFFSET); - if (!preempt_trace() && irq_trace()) - stop_critical_timing(a0, a1); + /* Use PREEMPT_DISABLE_OFFSET to handle !CONFIG_PREEMPT cases */ + pc -= PREEMPT_DISABLE_OFFSET; - preempt_disable_notrace(); + if (!preempt_trace(pc) && irq_trace()) + stop_critical_timing(a0, a1, pc); } static void tracer_hardirqs_off(void *none, unsigned long a0, unsigned long a1) { + unsigned int pc = preempt_count(); + /* * Tracepoint probes are expected to be called with preempt disabled, * We don't care about being called with preempt disabled but we need * to know in the future if that changes so we can remove the next * preempt_enable. */ - WARN_ON_ONCE(!preempt_count()); - - /* Tracepoint probes disable preemption atleast once, account for that */ - preempt_enable_notrace(); + WARN_ON_ONCE(pc < PREEMPT_DISABLE_OFFSET); - if (!preempt_trace() && irq_trace()) - start_critical_timing(a0, a1); + /* Use PREEMPT_DISABLE_OFFSET to handle !CONFIG_PREEMPT cases */ + pc -= PREEMPT_DISABLE_OFFSET; - preempt_disable_notrace(); + if (!preempt_trace(pc) && irq_trace()) + start_critical_timing(a0, a1, pc); } static int irqsoff_tracer_init(struct trace_array *tr) @@ -679,14 +683,18 @@ static struct tracer irqsoff_tracer __read_mostly = #ifdef CONFIG_PREEMPT_TRACER static void tracer_preempt_on(void *none, unsigned long a0, unsigned long a1) { - if (preempt_trace() && !irq_trace()) - stop_critical_timing(a0, a1); + int pc = preempt_count(); + + if (preempt_trace(pc) && !irq_trace()) + stop_critical_timing(a0, a1, pc); } static void tracer_preempt_off(void *none, unsigned long a0, unsigned long a1) { - if (preempt_trace() && !irq_trace()) - start_critical_timing(a0, a1); + int pc = preempt_count(); + + if (preempt_trace(pc) && !irq_trace()) + start_critical_timing(a0, a1, pc); } static int preemptoff_tracer_init(struct trace_array *tr) -- cgit v1.2.1