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tracing: Minor last minute fixes

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- 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
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Merge tag 'trace-fixes-v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracing fixes from Steven Rostedt:
 "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"

* tag 'trace-fixes-v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  rv: Update rv_en(dis)able_monitor doc to match kernel-doc
  tracing: Add MODULE_DESCRIPTION() to preemptirq_delay_test
  ring-buffer: Fix a race between readers and resize checks
  ring-buffer: Correct stale comments related to non-consuming readers
This commit is contained in:
Linus Torvalds 2024-05-23 12:36:38 -07:00
commit 404001ddf3
3 changed files with 15 additions and 13 deletions
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1
kernel/trace/preemptirq_delay_test.c
View File

@ -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");

25
kernel/trace/ring_buffer.c
View File

@ -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);

2
kernel/trace/rv/rv.c
View File

@ -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.
*/