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authorPetr Pavlu <petr.pavlu@suse.com>2023-12-05 17:17:35 +0100
committerSteven Rostedt (Google) <rostedt@goodmis.org>2023-12-05 17:16:48 -0500
commit34209fe83ef8404353f91ab4ea4035dbc9922d04 (patch)
tree716f72d2c318ba012b4d612a0966a3401ff09df1 /kernel/trace/trace.c
parent7fed14f7ac9cf5e38c693836fe4a874720141845 (diff)
tracing: Fix a warning when allocating buffered events fails
Function trace_buffered_event_disable() produces an unexpected warning when the previous call to trace_buffered_event_enable() fails to allocate pages for buffered events. The situation can occur as follows: * The counter trace_buffered_event_ref is at 0. * The soft mode gets enabled for some event and trace_buffered_event_enable() is called. The function increments trace_buffered_event_ref to 1 and starts allocating event pages. * The allocation fails for some page and trace_buffered_event_disable() is called for cleanup. * Function trace_buffered_event_disable() decrements trace_buffered_event_ref back to 0, recognizes that it was the last use of buffered events and frees all allocated pages. * The control goes back to trace_buffered_event_enable() which returns. The caller of trace_buffered_event_enable() has no information that the function actually failed. * Some time later, the soft mode is disabled for the same event. Function trace_buffered_event_disable() is called. It warns on "WARN_ON_ONCE(!trace_buffered_event_ref)" and returns. Buffered events are just an optimization and can handle failures. Make trace_buffered_event_enable() exit on the first failure and left any cleanup later to when trace_buffered_event_disable() is called. Link: https://lore.kernel.org/all/20231127151248.7232-2-petr.pavlu@suse.com/ Link: https://lkml.kernel.org/r/20231205161736.19663-3-petr.pavlu@suse.com Fixes: 0fc1b09ff1ff ("tracing: Use temp buffer when filtering events") Signed-off-by: Petr Pavlu <petr.pavlu@suse.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/trace.c')
-rw-r--r--kernel/trace/trace.c11
1 files changed, 5 insertions, 6 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 6aeffa4a6994..ef72354f61ce 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2728,8 +2728,11 @@ void trace_buffered_event_enable(void)
for_each_tracing_cpu(cpu) {
page = alloc_pages_node(cpu_to_node(cpu),
GFP_KERNEL | __GFP_NORETRY, 0);
- if (!page)
- goto failed;
+ /* This is just an optimization and can handle failures */
+ if (!page) {
+ pr_err("Failed to allocate event buffer\n");
+ break;
+ }
event = page_address(page);
memset(event, 0, sizeof(*event));
@@ -2743,10 +2746,6 @@ void trace_buffered_event_enable(void)
WARN_ON_ONCE(1);
preempt_enable();
}
-
- return;
- failed:
- trace_buffered_event_disable();
}
static void enable_trace_buffered_event(void *data)