Linus,
tracing: Minor last minute fixes
- Fix a very tight race between the ring buffer readers and resizing
the ring buffer.
- Correct some stale comments in the ring buffer code.
- Fix kernel-doc in the rv code.
- Add a MODULE_DESCRIPTION to preemptirq_delay_test
Please pull the latest trace-fixes-v6.10 tree, which can be found at:
git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
trace-fixes-v6.10
Tag SHA1: 53ad9da2f490bc02e45f44bc2a33d4c3b6b78c6b
Head SHA1: 1e8b7b3dbb3103d577a586ca72bc329f7b67120b
Jeff Johnson (1):
tracing: Add MODULE_DESCRIPTION() to preemptirq_delay_test
Petr Pavlu (2):
ring-buffer: Correct stale comments related to non-consuming readers
ring-buffer: Fix a race between readers and resize checks
Yang Li (1):
rv: Update rv_en(dis)able_monitor doc to match kernel-doc
----
kernel/trace/preemptirq_delay_test.c | 1 +
kernel/trace/ring_buffer.c | 25 ++++++++++++-------------
kernel/trace/rv/rv.c | 2 ++
3 files changed, 15 insertions(+), 13 deletions(-)
---------------------------
diff --git a/kernel/trace/preemptirq_delay_test.c b/kernel/trace/preemptirq_delay_test.c
index 8c4ffd076162..cb0871fbdb07 100644
--- a/kernel/trace/preemptirq_delay_test.c
+++ b/kernel/trace/preemptirq_delay_test.c
@@ -215,4 +215,5 @@ static void __exit preemptirq_delay_exit(void)
module_init(preemptirq_delay_init)
module_exit(preemptirq_delay_exit)
+MODULE_DESCRIPTION("Preempt / IRQ disable delay thread to test latency tracers");
MODULE_LICENSE("GPL v2");
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 7345a8b625fb..28853966aa9a 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1460,6 +1460,11 @@ static void rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
*
* As a safety measure we check to make sure the data pages have not
* been corrupted.
+ *
+ * Callers of this function need to guarantee that the list of pages doesn't get
+ * modified during the check. In particular, if it's possible that the function
+ * is invoked with concurrent readers which can swap in a new reader page then
+ * the caller should take cpu_buffer->reader_lock.
*/
static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
{
@@ -2210,8 +2215,12 @@ int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
*/
synchronize_rcu();
for_each_buffer_cpu(buffer, cpu) {
+ unsigned long flags;
+
cpu_buffer = buffer->buffers[cpu];
+ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
rb_check_pages(cpu_buffer);
+ raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
}
atomic_dec(&buffer->record_disabled);
}
@@ -5046,13 +5055,9 @@ EXPORT_SYMBOL_GPL(ring_buffer_consume);
* @flags: gfp flags to use for memory allocation
*
* This performs the initial preparations necessary to iterate
- * through the buffer. Memory is allocated, buffer recording
+ * through the buffer. Memory is allocated, buffer resizing
* is disabled, and the iterator pointer is returned to the caller.
*
- * Disabling buffer recording prevents the reading from being
- * corrupted. This is not a consuming read, so a producer is not
- * expected.
- *
* After a sequence of ring_buffer_read_prepare calls, the user is
* expected to make at least one call to ring_buffer_read_prepare_sync.
* Afterwards, ring_buffer_read_start is invoked to get things going
@@ -5139,8 +5144,7 @@ EXPORT_SYMBOL_GPL(ring_buffer_read_start);
* ring_buffer_read_finish - finish reading the iterator of the buffer
* @iter: The iterator retrieved by ring_buffer_start
*
- * This re-enables the recording to the buffer, and frees the
- * iterator.
+ * This re-enables resizing of the buffer, and frees the iterator.
*/
void
ring_buffer_read_finish(struct ring_buffer_iter *iter)
@@ -5148,12 +5152,7 @@ ring_buffer_read_finish(struct ring_buffer_iter *iter)
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
unsigned long flags;
- /*
- * Ring buffer is disabled from recording, here's a good place
- * to check the integrity of the ring buffer.
- * Must prevent readers from trying to read, as the check
- * clears the HEAD page and readers require it.
- */
+ /* Use this opportunity to check the integrity of the ring buffer. */
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
rb_check_pages(cpu_buffer);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
diff --git a/kernel/trace/rv/rv.c b/kernel/trace/rv/rv.c
index 2f68e93fff0b..df0745a42a3f 100644
--- a/kernel/trace/rv/rv.c
+++ b/kernel/trace/rv/rv.c
@@ -245,6 +245,7 @@ static int __rv_disable_monitor(struct rv_monitor_def *mdef, bool sync)
/**
* rv_disable_monitor - disable a given runtime monitor
+ * @mdef: Pointer to the monitor definition structure.
*
* Returns 0 on success.
*/
@@ -256,6 +257,7 @@ int rv_disable_monitor(struct rv_monitor_def *mdef)
/**
* rv_enable_monitor - enable a given runtime monitor
+ * @mdef: Pointer to the monitor definition structure.
*
* Returns 0 on success, error otherwise.
*/
The pull request you sent on Thu, 23 May 2024 12:36:40 -0400:
> git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git trace-fixes-v6.10
has been merged into torvalds/linux.git:
https://git.kernel.org/torvalds/c/404001ddf3e40369510a08b8b7e895c2da692b79
Thank you!
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