diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2024-11-16 08:12:43 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2024-11-16 08:12:43 -0800 |
commit | b5a24181e461e8bfa8cdf35e1804679dc1bebcdd (patch) | |
tree | f45b614132f0454cf37cf36a9fe496c598ef9242 | |
parent | e8bdb3c8be08c9a3edc0a373c0aa8729355a0705 (diff) | |
parent | 09663753bb7c50b33f8e5fa562c20ce275b88237 (diff) |
Merge tag 'trace-ringbuffer-v6.12-rc7-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull ring buffer fixes from Steven Rostedt:
- Revert: "ring-buffer: Do not have boot mapped buffers hook to CPU
hotplug"
A crash that happened on cpu hotplug was actually caused by the
incorrect ref counting that was fixed by commit 2cf9733891a4
("ring-buffer: Fix refcount setting of boot mapped buffers"). The
removal of calling cpu hotplug callbacks on memory mapped buffers was
not an issue even though the tests at the time pointed toward it. But
in fact, there's a check in that code that tests to see if the
buffers are already allocated or not, and will not allocate them
again if they are. Not calling the cpu hotplug callbacks ended up not
initializing the non boot CPU buffers.
Simply remove that change.
- Clear all CPU buffers when starting tracing in a boot mapped buffer
To properly process events from a previous boot, the address space
needs to be accounted for due to KASLR and the events in the buffer
are updated accordingly when read. This also requires that when the
buffer has tracing enabled again in the current boot that the buffers
are reset so that events from the previous boot do not interact with
the events of the current boot and cause confusing due to not having
the proper meta data.
It was found that if a CPU is taken offline, that its per CPU buffer
is not reset when tracing starts. This allows for events to be from
both the previous boot and the current boot to be in the buffer at
the same time. Clear all CPU buffers when tracing is started in a
boot mapped buffer.
* tag 'trace-ringbuffer-v6.12-rc7-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
tracing/ring-buffer: Clear all memory mapped CPU ring buffers on first recording
Revert: "ring-buffer: Do not have boot mapped buffers hook to CPU hotplug"
-rw-r--r-- | kernel/trace/ring_buffer.c | 9 | ||||
-rw-r--r-- | kernel/trace/trace.c | 28 |
2 files changed, 29 insertions, 8 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 3ea4f7bb1837..5807116bcd0b 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -2337,12 +2337,9 @@ static struct trace_buffer *alloc_buffer(unsigned long size, unsigned flags, if (!buffer->buffers[cpu]) goto fail_free_buffers; - /* If already mapped, do not hook to CPU hotplug */ - if (!start) { - ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); - if (ret < 0) - goto fail_free_buffers; - } + ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); + if (ret < 0) + goto fail_free_buffers; mutex_init(&buffer->mutex); diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 2b64b3ec67d9..6a891e00aa7f 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2386,6 +2386,25 @@ void tracing_reset_online_cpus(struct array_buffer *buf) ring_buffer_record_enable(buffer); } +static void tracing_reset_all_cpus(struct array_buffer *buf) +{ + struct trace_buffer *buffer = buf->buffer; + + if (!buffer) + return; + + ring_buffer_record_disable(buffer); + + /* Make sure all commits have finished */ + synchronize_rcu(); + + buf->time_start = buffer_ftrace_now(buf, buf->cpu); + + ring_buffer_reset(buffer); + + ring_buffer_record_enable(buffer); +} + /* Must have trace_types_lock held */ void tracing_reset_all_online_cpus_unlocked(void) { @@ -6145,8 +6164,13 @@ static void update_last_data(struct trace_array *tr) if (!tr->text_delta && !tr->data_delta) return; - /* Clear old data */ - tracing_reset_online_cpus(&tr->array_buffer); + /* + * Need to clear all CPU buffers as there cannot be events + * from the previous boot mixed with events with this boot + * as that will cause a confusing trace. Need to clear all + * CPU buffers, even for those that may currently be offline. + */ + tracing_reset_all_cpus(&tr->array_buffer); /* Using current data now */ tr->text_delta = 0; |