| Message ID | 20241011112850.17212b25@gandalf.local.home (mailing list archive) |
|---|---|
| State | Rejected |
| Headers | show |
| Series | ring-buffer: Synchronize ring_buffer_subbuf_order_set() with rb_check_pages() | expand |
On Fri, 11 Oct 2024 11:28:50 -0400 Steven Rostedt <rostedt@goodmis.org> wrote: > From: Steven Rostedt <rostedt@goodmis.org> > > The rb_check_pages() scans the ring buffer sub buffers to make sure they > are valid after an update. But locks are released during the update to not > hold preemption for too long. > > The ring_buffer_subbuf_order_set() updates the counter used by > rb_check_pages() without any locks. But it also updates the pages. Even > though it is likely that the buffer->mutex is enough to protect this, but > since rb_check_pages() uses the cpu_buffer->reader_lock for > synchronization, take that lock as well when updating the pages and > counter in ring_buffer_subbuf_order_set(). > > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> I rejected this patch as I believe the version Petr has is required. -- Steve > --- > Note, this is based on top of: > > https://lore.kernel.org/linux-trace-kernel/20240715145141.5528-1-petr.pavlu@suse.com/ > > kernel/trace/ring_buffer.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index 696d422d5b35..0672df07b599 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -6774,6 +6774,7 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) > } > > for_each_buffer_cpu(buffer, cpu) { > + unsigned long flags; > > if (!cpumask_test_cpu(cpu, buffer->cpumask)) > continue; > @@ -6800,11 +6801,15 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) > struct buffer_page, list); > list_del_init(&cpu_buffer->reader_page->list); > > + /* Synchronize with rb_check_pages() */ > + raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); > + > /* The cpu_buffer pages are a link list with no head */ > cpu_buffer->pages = cpu_buffer->new_pages.next; > cpu_buffer->new_pages.next->prev = cpu_buffer->new_pages.prev; > cpu_buffer->new_pages.prev->next = cpu_buffer->new_pages.next; > cpu_buffer->cnt++; > + raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); > > /* Clear the new_pages list */ > INIT_LIST_HEAD(&cpu_buffer->new_pages);
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 696d422d5b35..0672df07b599 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -6774,6 +6774,7 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) } for_each_buffer_cpu(buffer, cpu) { + unsigned long flags; if (!cpumask_test_cpu(cpu, buffer->cpumask)) continue; @@ -6800,11 +6801,15 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) struct buffer_page, list); list_del_init(&cpu_buffer->reader_page->list); + /* Synchronize with rb_check_pages() */ + raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); + /* The cpu_buffer pages are a link list with no head */ cpu_buffer->pages = cpu_buffer->new_pages.next; cpu_buffer->new_pages.next->prev = cpu_buffer->new_pages.prev; cpu_buffer->new_pages.prev->next = cpu_buffer->new_pages.next; cpu_buffer->cnt++; + raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); /* Clear the new_pages list */ INIT_LIST_HEAD(&cpu_buffer->new_pages);