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authorLinus Torvalds <torvalds@linux-foundation.org>2014-12-16 12:53:59 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-12-16 12:53:59 -0800
commita7c180aa7e76a55642e8492f28353303a50292c2 (patch)
treeb80b3575f1717a5e3a07081b5c9409805662490d
parent2dbfca5a181973558277b28b1f4c36362291f5e0 (diff)
parent0daa2302968c13b657118d6ac92471f8fd2f3f28 (diff)
Merge tag 'trace-3.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing updates from Steven Rostedt: "As the merge window is still open, and this code was not as complex as I thought it might be. I'm pushing this in now. This will allow Thomas to debug his irq work for 3.20. This adds two new features: 1) Allow traceopoints to be enabled right after mm_init(). By passing in the trace_event= kernel command line parameter, tracepoints can be enabled at boot up. For debugging things like the initialization of interrupts, it is needed to have tracepoints enabled very early. People have asked about this before and this has been on my todo list. As it can be helpful for Thomas to debug his upcoming 3.20 IRQ work, I'm pushing this now. This way he can add tracepoints into the IRQ set up and have users enable them when things go wrong. 2) Have the tracepoints printed via printk() (the console) when they are triggered. If the irq code locks up or reboots the box, having the tracepoint output go into the kernel ring buffer is useless for debugging. But being able to add the tp_printk kernel command line option along with the trace_event= option will have these tracepoints printed as they occur, and that can be really useful for debugging early lock up or reboot problems. This code is not that intrusive and it passed all my tests. Thomas tried them out too and it works for his needs. Link: http://lkml.kernel.org/r/20141214201609.126831471@goodmis.org" * tag 'trace-3.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing: Add tp_printk cmdline to have tracepoints go to printk() tracing: Move enabling tracepoints to just after rcu_init()
-rw-r--r--Documentation/kernel-parameters.txt18
-rw-r--r--include/linux/ftrace.h7
-rw-r--r--init/main.c4
-rw-r--r--kernel/sysctl.c7
-rw-r--r--kernel/trace/trace.c25
-rw-r--r--kernel/trace/trace.h14
-rw-r--r--kernel/trace/trace_events.c42
-rw-r--r--kernel/trace/trace_syscalls.c7
8 files changed, 116 insertions, 8 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 1de833556d22..bda85f1dbd44 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3570,6 +3570,24 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
See also Documentation/trace/ftrace.txt "trace options"
section.
+ tp_printk[FTRACE]
+ Have the tracepoints sent to printk as well as the
+ tracing ring buffer. This is useful for early boot up
+ where the system hangs or reboots and does not give the
+ option for reading the tracing buffer or performing a
+ ftrace_dump_on_oops.
+
+ To turn off having tracepoints sent to printk,
+ echo 0 > /proc/sys/kernel/tracepoint_printk
+ Note, echoing 1 into this file without the
+ tracepoint_printk kernel cmdline option has no effect.
+
+ ** CAUTION **
+
+ Having tracepoints sent to printk() and activating high
+ frequency tracepoints such as irq or sched, can cause
+ the system to live lock.
+
traceoff_on_warning
[FTRACE] enable this option to disable tracing when a
warning is hit. This turns off "tracing_on". Tracing can
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index ed501953f0b2..1da602982cf9 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -39,6 +39,12 @@
# define FTRACE_FORCE_LIST_FUNC 0
#endif
+/* Main tracing buffer and events set up */
+#ifdef CONFIG_TRACING
+void trace_init(void);
+#else
+static inline void trace_init(void) { }
+#endif
struct module;
struct ftrace_hash;
@@ -873,6 +879,7 @@ static inline int test_tsk_trace_graph(struct task_struct *tsk)
enum ftrace_dump_mode;
extern enum ftrace_dump_mode ftrace_dump_on_oops;
+extern int tracepoint_printk;
extern void disable_trace_on_warning(void);
extern int __disable_trace_on_warning;
diff --git a/init/main.c b/init/main.c
index 8a914b758e5d..747ecc4c0a19 100644
--- a/init/main.c
+++ b/init/main.c
@@ -578,6 +578,10 @@ asmlinkage __visible void __init start_kernel(void)
local_irq_disable();
idr_init_cache();
rcu_init();
+
+ /* trace_printk() and trace points may be used after this */
+ trace_init();
+
context_tracking_init();
radix_tree_init();
/* init some links before init_ISA_irqs() */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 7c54ff79afd7..137c7f69b264 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -623,6 +623,13 @@ static struct ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = proc_dointvec,
},
+ {
+ .procname = "tracepoint_printk",
+ .data = &tracepoint_printk,
+ .maxlen = sizeof(tracepoint_printk),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ },
#endif
#ifdef CONFIG_KEXEC
{
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ab76b7bcb36a..2e767972e99c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -63,6 +63,10 @@ static bool __read_mostly tracing_selftest_running;
*/
bool __read_mostly tracing_selftest_disabled;
+/* Pipe tracepoints to printk */
+struct trace_iterator *tracepoint_print_iter;
+int tracepoint_printk;
+
/* For tracers that don't implement custom flags */
static struct tracer_opt dummy_tracer_opt[] = {
{ }
@@ -193,6 +197,13 @@ static int __init set_trace_boot_clock(char *str)
}
__setup("trace_clock=", set_trace_boot_clock);
+static int __init set_tracepoint_printk(char *str)
+{
+ if ((strcmp(str, "=0") != 0 && strcmp(str, "=off") != 0))
+ tracepoint_printk = 1;
+ return 1;
+}
+__setup("tp_printk", set_tracepoint_printk);
unsigned long long ns2usecs(cycle_t nsec)
{
@@ -6898,6 +6909,19 @@ out:
return ret;
}
+void __init trace_init(void)
+{
+ if (tracepoint_printk) {
+ tracepoint_print_iter =
+ kmalloc(sizeof(*tracepoint_print_iter), GFP_KERNEL);
+ if (WARN_ON(!tracepoint_print_iter))
+ tracepoint_printk = 0;
+ }
+ tracer_alloc_buffers();
+ init_ftrace_syscalls();
+ trace_event_init();
+}
+
__init static int clear_boot_tracer(void)
{
/*
@@ -6917,6 +6941,5 @@ __init static int clear_boot_tracer(void)
return 0;
}
-early_initcall(tracer_alloc_buffers);
fs_initcall(tracer_init_debugfs);
late_initcall(clear_boot_tracer);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 3255dfb054a0..8de48bac1ce2 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1301,4 +1301,18 @@ int perf_ftrace_event_register(struct ftrace_event_call *call,
#define perf_ftrace_event_register NULL
#endif
+#ifdef CONFIG_FTRACE_SYSCALLS
+void init_ftrace_syscalls(void);
+#else
+static inline void init_ftrace_syscalls(void) { }
+#endif
+
+#ifdef CONFIG_EVENT_TRACING
+void trace_event_init(void);
+#else
+static inline void __init trace_event_init(void) { }
+#endif
+
+extern struct trace_iterator *tracepoint_print_iter;
+
#endif /* _LINUX_KERNEL_TRACE_H */
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index d0e4f92b5eb6..366a78a3e61e 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -212,8 +212,40 @@ void *ftrace_event_buffer_reserve(struct ftrace_event_buffer *fbuffer,
}
EXPORT_SYMBOL_GPL(ftrace_event_buffer_reserve);
+static DEFINE_SPINLOCK(tracepoint_iter_lock);
+
+static void output_printk(struct ftrace_event_buffer *fbuffer)
+{
+ struct ftrace_event_call *event_call;
+ struct trace_event *event;
+ unsigned long flags;
+ struct trace_iterator *iter = tracepoint_print_iter;
+
+ if (!iter)
+ return;
+
+ event_call = fbuffer->ftrace_file->event_call;
+ if (!event_call || !event_call->event.funcs ||
+ !event_call->event.funcs->trace)
+ return;
+
+ event = &fbuffer->ftrace_file->event_call->event;
+
+ spin_lock_irqsave(&tracepoint_iter_lock, flags);
+ trace_seq_init(&iter->seq);
+ iter->ent = fbuffer->entry;
+ event_call->event.funcs->trace(iter, 0, event);
+ trace_seq_putc(&iter->seq, 0);
+ printk("%s", iter->seq.buffer);
+
+ spin_unlock_irqrestore(&tracepoint_iter_lock, flags);
+}
+
void ftrace_event_buffer_commit(struct ftrace_event_buffer *fbuffer)
{
+ if (tracepoint_printk)
+ output_printk(fbuffer);
+
event_trigger_unlock_commit(fbuffer->ftrace_file, fbuffer->buffer,
fbuffer->event, fbuffer->entry,
fbuffer->flags, fbuffer->pc);
@@ -2480,8 +2512,14 @@ static __init int event_trace_init(void)
#endif
return 0;
}
-early_initcall(event_trace_memsetup);
-core_initcall(event_trace_enable);
+
+void __init trace_event_init(void)
+{
+ event_trace_memsetup();
+ init_ftrace_syscalls();
+ event_trace_enable();
+}
+
fs_initcall(event_trace_init);
#ifdef CONFIG_FTRACE_STARTUP_TEST
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index dfe00a4f3f3e..c6ee36fcbf90 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -514,7 +514,7 @@ unsigned long __init __weak arch_syscall_addr(int nr)
return (unsigned long)sys_call_table[nr];
}
-static int __init init_ftrace_syscalls(void)
+void __init init_ftrace_syscalls(void)
{
struct syscall_metadata *meta;
unsigned long addr;
@@ -524,7 +524,7 @@ static int __init init_ftrace_syscalls(void)
GFP_KERNEL);
if (!syscalls_metadata) {
WARN_ON(1);
- return -ENOMEM;
+ return;
}
for (i = 0; i < NR_syscalls; i++) {
@@ -536,10 +536,7 @@ static int __init init_ftrace_syscalls(void)
meta->syscall_nr = i;
syscalls_metadata[i] = meta;
}
-
- return 0;
}
-early_initcall(init_ftrace_syscalls);
#ifdef CONFIG_PERF_EVENTS