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authorSteven Rostedt <srostedt@redhat.com>2008-11-21 12:41:55 -0500
committerIngo Molnar <mingo@elte.hu>2008-11-23 05:44:37 -0500
commit033601a32b2012b6948e80e739cca40bff4de4a0 (patch)
tree79f5fb4de0c76472174a1fd46c28e1503ac88dfc /kernel
parenta0a70c735ef714fe1b6777b571630c3d50c7b008 (diff)
ring-buffer: add tracing_off_permanent
Impact: feature to permanently disable ring buffer This patch adds a API to the ring buffer code that will permanently disable the ring buffer from ever recording. This should only be called when some serious anomaly is detected, and the system may be in an unstable state. When that happens, shutting down the recording to the ring buffers may be appropriate. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/ring_buffer.c79
1 files changed, 66 insertions, 13 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 85ced143c2c4..e206951603c1 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -18,8 +18,46 @@
18 18
19#include "trace.h" 19#include "trace.h"
20 20
21/* Global flag to disable all recording to ring buffers */ 21/*
22static int ring_buffers_off __read_mostly; 22 * A fast way to enable or disable all ring buffers is to
23 * call tracing_on or tracing_off. Turning off the ring buffers
24 * prevents all ring buffers from being recorded to.
25 * Turning this switch on, makes it OK to write to the
26 * ring buffer, if the ring buffer is enabled itself.
27 *
28 * There's three layers that must be on in order to write
29 * to the ring buffer.
30 *
31 * 1) This global flag must be set.
32 * 2) The ring buffer must be enabled for recording.
33 * 3) The per cpu buffer must be enabled for recording.
34 *
35 * In case of an anomaly, this global flag has a bit set that
36 * will permantly disable all ring buffers.
37 */
38
39/*
40 * Global flag to disable all recording to ring buffers
41 * This has two bits: ON, DISABLED
42 *
43 * ON DISABLED
44 * ---- ----------
45 * 0 0 : ring buffers are off
46 * 1 0 : ring buffers are on
47 * X 1 : ring buffers are permanently disabled
48 */
49
50enum {
51 RB_BUFFERS_ON_BIT = 0,
52 RB_BUFFERS_DISABLED_BIT = 1,
53};
54
55enum {
56 RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT,
57 RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT,
58};
59
60static long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
23 61
24/** 62/**
25 * tracing_on - enable all tracing buffers 63 * tracing_on - enable all tracing buffers
@@ -29,7 +67,7 @@ static int ring_buffers_off __read_mostly;
29 */ 67 */
30void tracing_on(void) 68void tracing_on(void)
31{ 69{
32 ring_buffers_off = 0; 70 set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
33} 71}
34 72
35/** 73/**
@@ -42,7 +80,18 @@ void tracing_on(void)
42 */ 80 */
43void tracing_off(void) 81void tracing_off(void)
44{ 82{
45 ring_buffers_off = 1; 83 clear_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
84}
85
86/**
87 * tracing_off_permanent - permanently disable ring buffers
88 *
89 * This function, once called, will disable all ring buffers
90 * permanenty.
91 */
92void tracing_off_permanent(void)
93{
94 set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
46} 95}
47 96
48#include "trace.h" 97#include "trace.h"
@@ -1185,7 +1234,7 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer,
1185 struct ring_buffer_event *event; 1234 struct ring_buffer_event *event;
1186 int cpu, resched; 1235 int cpu, resched;
1187 1236
1188 if (ring_buffers_off) 1237 if (ring_buffer_flags != RB_BUFFERS_ON)
1189 return NULL; 1238 return NULL;
1190 1239
1191 if (atomic_read(&buffer->record_disabled)) 1240 if (atomic_read(&buffer->record_disabled))
@@ -1297,7 +1346,7 @@ int ring_buffer_write(struct ring_buffer *buffer,
1297 int ret = -EBUSY; 1346 int ret = -EBUSY;
1298 int cpu, resched; 1347 int cpu, resched;
1299 1348
1300 if (ring_buffers_off) 1349 if (ring_buffer_flags != RB_BUFFERS_ON)
1301 return -EBUSY; 1350 return -EBUSY;
1302 1351
1303 if (atomic_read(&buffer->record_disabled)) 1352 if (atomic_read(&buffer->record_disabled))
@@ -2178,12 +2227,14 @@ static ssize_t
2178rb_simple_read(struct file *filp, char __user *ubuf, 2227rb_simple_read(struct file *filp, char __user *ubuf,
2179 size_t cnt, loff_t *ppos) 2228 size_t cnt, loff_t *ppos)
2180{ 2229{
2181 int *p = filp->private_data; 2230 long *p = filp->private_data;
2182 char buf[64]; 2231 char buf[64];
2183 int r; 2232 int r;
2184 2233
2185 /* !ring_buffers_off == tracing_on */ 2234 if (test_bit(RB_BUFFERS_DISABLED_BIT, p))
2186 r = sprintf(buf, "%d\n", !*p); 2235 r = sprintf(buf, "permanently disabled\n");
2236 else
2237 r = sprintf(buf, "%d\n", test_bit(RB_BUFFERS_ON_BIT, p));
2187 2238
2188 return simple_read_from_buffer(ubuf, cnt, ppos, buf, r); 2239 return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
2189} 2240}
@@ -2192,7 +2243,7 @@ static ssize_t
2192rb_simple_write(struct file *filp, const char __user *ubuf, 2243rb_simple_write(struct file *filp, const char __user *ubuf,
2193 size_t cnt, loff_t *ppos) 2244 size_t cnt, loff_t *ppos)
2194{ 2245{
2195 int *p = filp->private_data; 2246 long *p = filp->private_data;
2196 char buf[64]; 2247 char buf[64];
2197 long val; 2248 long val;
2198 int ret; 2249 int ret;
@@ -2209,8 +2260,10 @@ rb_simple_write(struct file *filp, const char __user *ubuf,
2209 if (ret < 0) 2260 if (ret < 0)
2210 return ret; 2261 return ret;
2211 2262
2212 /* !ring_buffers_off == tracing_on */ 2263 if (val)
2213 *p = !val; 2264 set_bit(RB_BUFFERS_ON_BIT, p);
2265 else
2266 clear_bit(RB_BUFFERS_ON_BIT, p);
2214 2267
2215 (*ppos)++; 2268 (*ppos)++;
2216 2269
@@ -2232,7 +2285,7 @@ static __init int rb_init_debugfs(void)
2232 d_tracer = tracing_init_dentry(); 2285 d_tracer = tracing_init_dentry();
2233 2286
2234 entry = debugfs_create_file("tracing_on", 0644, d_tracer, 2287 entry = debugfs_create_file("tracing_on", 0644, d_tracer,
2235 &ring_buffers_off, &rb_simple_fops); 2288 &ring_buffer_flags, &rb_simple_fops);
2236 if (!entry) 2289 if (!entry)
2237 pr_warning("Could not create debugfs 'tracing_on' entry\n"); 2290 pr_warning("Could not create debugfs 'tracing_on' entry\n");
2238 2291