tracing: Add alloc_snapshot kernel command line parameter
If debugging the kernel, and the developer wants to use
tracing_snapshot() in places where tracing_snapshot_alloc() may
be difficult (or more likely, the developer is lazy and doesn't
want to bother with tracing_snapshot_alloc() at all), then adding
alloc_snapshot
to the kernel command line parameter will tell ftrace to allocate
the snapshot buffer (if configured) when it allocates the main
tracing buffer.
I also noticed that ring_buffer_expanded and tracing_selftest_disabled
had inconsistent use of boolean "true" and "false" with "0" and "1".
I cleaned that up too.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 6c72381..0edc409 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -320,6 +320,13 @@
on: enable for both 32- and 64-bit processes
off: disable for both 32- and 64-bit processes
+ alloc_snapshot [FTRACE]
+ Allocate the ftrace snapshot buffer on boot up when the
+ main buffer is allocated. This is handy if debugging
+ and you need to use tracing_snapshot() on boot up, and
+ do not want to use tracing_snapshot_alloc() as it needs
+ to be done where GFP_KERNEL allocations are allowed.
+
amd_iommu= [HW,X86-64]
Pass parameters to the AMD IOMMU driver in the system.
Possible values are:
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 57b4220..4021a5e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -47,7 +47,7 @@
* On boot up, the ring buffer is set to the minimum size, so that
* we do not waste memory on systems that are not using tracing.
*/
-int ring_buffer_expanded;
+bool ring_buffer_expanded;
/*
* We need to change this state when a selftest is running.
@@ -121,12 +121,14 @@
static char bootup_tracer_buf[MAX_TRACER_SIZE] __initdata;
static char *default_bootup_tracer;
+static bool allocate_snapshot;
+
static int __init set_cmdline_ftrace(char *str)
{
strncpy(bootup_tracer_buf, str, MAX_TRACER_SIZE);
default_bootup_tracer = bootup_tracer_buf;
/* We are using ftrace early, expand it */
- ring_buffer_expanded = 1;
+ ring_buffer_expanded = true;
return 1;
}
__setup("ftrace=", set_cmdline_ftrace);
@@ -147,6 +149,15 @@
}
__setup("ftrace_dump_on_oops", set_ftrace_dump_on_oops);
+static int __init alloc_snapshot(char *str)
+{
+ allocate_snapshot = true;
+ /* We also need the main ring buffer expanded */
+ ring_buffer_expanded = true;
+ return 1;
+}
+__setup("alloc_snapshot", alloc_snapshot);
+
static char trace_boot_options_buf[MAX_TRACER_SIZE] __initdata;
static char *trace_boot_options __initdata;
@@ -951,7 +962,7 @@
tracing_set_tracer(type->name);
default_bootup_tracer = NULL;
/* disable other selftests, since this will break it. */
- tracing_selftest_disabled = 1;
+ tracing_selftest_disabled = true;
#ifdef CONFIG_FTRACE_STARTUP_TEST
printk(KERN_INFO "Disabling FTRACE selftests due to running tracer '%s'\n",
type->name);
@@ -3318,7 +3329,7 @@
* we use the size that was given, and we can forget about
* expanding it later.
*/
- ring_buffer_expanded = 1;
+ ring_buffer_expanded = true;
/* May be called before buffers are initialized */
if (!tr->trace_buffer.buffer)
@@ -5396,53 +5407,57 @@
}
}
-static int allocate_trace_buffers(struct trace_array *tr, int size)
+static int
+allocate_trace_buffer(struct trace_array *tr, struct trace_buffer *buf, int size)
{
enum ring_buffer_flags rb_flags;
rb_flags = trace_flags & TRACE_ITER_OVERWRITE ? RB_FL_OVERWRITE : 0;
- tr->trace_buffer.buffer = ring_buffer_alloc(size, rb_flags);
- if (!tr->trace_buffer.buffer)
- goto out_free;
+ buf->buffer = ring_buffer_alloc(size, rb_flags);
+ if (!buf->buffer)
+ return -ENOMEM;
- tr->trace_buffer.data = alloc_percpu(struct trace_array_cpu);
- if (!tr->trace_buffer.data)
- goto out_free;
+ buf->data = alloc_percpu(struct trace_array_cpu);
+ if (!buf->data) {
+ ring_buffer_free(buf->buffer);
+ return -ENOMEM;
+ }
- init_trace_buffers(tr, &tr->trace_buffer);
+ init_trace_buffers(tr, buf);
/* Allocate the first page for all buffers */
set_buffer_entries(&tr->trace_buffer,
ring_buffer_size(tr->trace_buffer.buffer, 0));
+ return 0;
+}
+
+static int allocate_trace_buffers(struct trace_array *tr, int size)
+{
+ int ret;
+
+ ret = allocate_trace_buffer(tr, &tr->trace_buffer, size);
+ if (ret)
+ return ret;
+
#ifdef CONFIG_TRACER_MAX_TRACE
+ ret = allocate_trace_buffer(tr, &tr->max_buffer,
+ allocate_snapshot ? size : 1);
+ if (WARN_ON(ret)) {
+ ring_buffer_free(tr->trace_buffer.buffer);
+ free_percpu(tr->trace_buffer.data);
+ return -ENOMEM;
+ }
+ tr->allocated_snapshot = allocate_snapshot;
- tr->max_buffer.buffer = ring_buffer_alloc(1, rb_flags);
- if (!tr->max_buffer.buffer)
- goto out_free;
-
- tr->max_buffer.data = alloc_percpu(struct trace_array_cpu);
- if (!tr->max_buffer.data)
- goto out_free;
-
- init_trace_buffers(tr, &tr->max_buffer);
-
- set_buffer_entries(&tr->max_buffer, 1);
+ /*
+ * Only the top level trace array gets its snapshot allocated
+ * from the kernel command line.
+ */
+ allocate_snapshot = false;
#endif
return 0;
-
- out_free:
- if (tr->trace_buffer.buffer)
- ring_buffer_free(tr->trace_buffer.buffer);
- free_percpu(tr->trace_buffer.data);
-
-#ifdef CONFIG_TRACER_MAX_TRACE
- if (tr->max_buffer.buffer)
- ring_buffer_free(tr->max_buffer.buffer);
- free_percpu(tr->max_buffer.data);
-#endif
- return -ENOMEM;
}
static int new_instance_create(const char *name)
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index f493182..26bc718 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -660,7 +660,7 @@
#define DYN_FTRACE_TEST_NAME2 trace_selftest_dynamic_test_func2
extern int DYN_FTRACE_TEST_NAME2(void);
-extern int ring_buffer_expanded;
+extern bool ring_buffer_expanded;
extern bool tracing_selftest_disabled;
DECLARE_PER_CPU(int, ftrace_cpu_disabled);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index a376ab5..38b54c5 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1844,8 +1844,8 @@
static __init int setup_trace_event(char *str)
{
strlcpy(bootup_event_buf, str, COMMAND_LINE_SIZE);
- ring_buffer_expanded = 1;
- tracing_selftest_disabled = 1;
+ ring_buffer_expanded = true;
+ tracing_selftest_disabled = true;
return 1;
}