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ring_buffer: tracing: Inherit the tracing setting to next ring buffer

Maintain the tracing on/off setting of the ring_buffer when switching to the trace buffer snapshot. Taking a snapshot is done by swapping the backup ring buffer (max_tr_buffer). But since the tracing on/off setting is defined by the ring buffer, when swapping it, the tracing on/off setting can also be changed. This causes a strange result like below: /sys/kernel/debug/tracing # cat tracing_on 1 /sys/kernel/debug/tracing # echo 0 > tracing_on /sys/kernel/debug/tracing # cat tracing_on 0 /sys/kernel/debug/tracing # echo 1 > snapshot /sys/kernel/debug/tracing # cat tracing_on 1 /sys/kernel/debug/tracing # echo 1 > snapshot /sys/kernel/debug/tracing # cat tracing_on 0 We don't touch tracing_on, but snapshot changes tracing_on setting each time. This is an anomaly, because user doesn't know that each "ring_buffer" stores its own tracing-enable state and the snapshot is done by swapping ring buffers. Link: http://lkml.kernel.org/r/153149929558.11274.11730609978254724394.stgit@devbox

Masami Hiramatsu committed 8 years ago

Commit 73c8d891 parent 1863c383 files · +23 −0Browse files

Unified · Split

3 files
  1. include/linux/ring_buffer.h +1 −0
  2. kernel/trace/ring_buffer.c +16 −0
  3. kernel/trace/trace.c +6 −0
include/linux/ring_buffer.h+1−0
@@ -165,6 +165,7 @@ void ring_buffer_record_enable(struct ring_buffer *buffer); · 164 unmodified lines
165void ring_buffer_record_off(struct ring_buffer *buffer);165void ring_buffer_record_off(struct ring_buffer *buffer);
166void ring_buffer_record_on(struct ring_buffer *buffer);166void ring_buffer_record_on(struct ring_buffer *buffer);
167int ring_buffer_record_is_on(struct ring_buffer *buffer);167int ring_buffer_record_is_on(struct ring_buffer *buffer);
168int ring_buffer_record_is_set_on(struct ring_buffer *buffer);
168void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu);169void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu);
169void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu);170void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu);
170 171
kernel/trace/ring_buffer.c+16−0
@@ -3226,6 +3226,22 @@ int ring_buffer_record_is_on(struct ring_buffer *buffer) · 3225 unmodified lines
3226 return !atomic_read(&buffer->record_disabled);3226 return !atomic_read(&buffer->record_disabled);
3227}3227}
3228 3228
3229/**
3230 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
3231 * @buffer: The ring buffer to see if write is set enabled
3232 *
3233 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
3234 * Note that this does NOT mean it is in a writable state.
3235 *
3236 * It may return true when the ring buffer has been disabled by
3237 * ring_buffer_record_disable(), as that is a temporary disabling of
3238 * the ring buffer.
3239 */
3240int ring_buffer_record_is_set_on(struct ring_buffer *buffer)
3241{
3242 return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
3243}
3244
3229/**3245/**
3230 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer3246 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3231 * @buffer: The ring buffer to stop writes to.3247 * @buffer: The ring buffer to stop writes to.
kernel/trace/trace.c+6−0
@@ -1373,6 +1373,12 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu) · 1372 unmodified lines
1373 1373
1374 arch_spin_lock(&tr->max_lock);1374 arch_spin_lock(&tr->max_lock);
1375 1375
1376 /* Inherit the recordable setting from trace_buffer */
1377 if (ring_buffer_record_is_set_on(tr->trace_buffer.buffer))
1378 ring_buffer_record_on(tr->max_buffer.buffer);
1379 else
1380 ring_buffer_record_off(tr->max_buffer.buffer);
1381
1376 swap(tr->trace_buffer.buffer, tr->max_buffer.buffer);1382 swap(tr->trace_buffer.buffer, tr->max_buffer.buffer);
1377 1383
1378 __update_max_tr(tr, tsk, cpu);1384 __update_max_tr(tr, tsk, cpu);