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Message-ID: <20260108133329.78a73fed@gandalf.local.home>
Date: Thu, 8 Jan 2026 13:33:29 -0500
From: Steven Rostedt <rostedt@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Masami Hiramatsu
<mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Ben Dooks <ben.dooks@...ethink.co.uk>, Julia Lawall
<Julia.Lawall@...ia.fr>, Wupeng Ma <mawupeng1@...wei.com>
Subject: [GIT PULL] tracing: Fixes for v6.19
Linus,
tracing fixes for v6.19:
- Remove useless assignment of soft_mode variable
The function __ftrace_event_enable_disable() sets "soft_mode" in one of
the branch paths but doesn't use it after that. Remove the setting of that
variable.
- Add a cond_resched() in ring_buffer_resize()
The resize function that allocates all the pages for the ring buffer was
causing a soft lockup on PREEMPT_NONE configs when allocating large
buffers on machines with many CPUs. Hopefully this is the last
cond_resched() needed to be added as PREEMPT_LAZY becomes the norm in the
future.
- Make ftrace_graph_ent depth field signed
The "depth" field of struct ftrace_graph_ent was converted from "int" to
"unsigned long" for alignment reasons to work with being embedded in other
structures. The conversion from a signed to unsigned caused integrity
checks to always pass as they were comparing "depth" to less than zero.
Make the field signed long.
- Add recursion protection to stack trace events
A infinite recursion was triggered by a stack trace event calling RCU
which internally called rcu_read_unlock_special(), which triggered an
event that was also doing stacktraces which cause it to trigger the same
RCU lock that called rcu_read_unlock_special() again.
Update the trace_test_and_set_recursion() to add a set of context checks
for events to use, and have the stack trace event use that for recursion
protection.
- Make the variable ftrace_dump_on_oops static
The cleanup of sysctl that moved all the updates to the files that use
them moved the reference of ftrace_dump_on_oops to where it is used.
It is no longer used outside of the trace.c file. Make it static.
Please pull the latest trace-v6.19-rc4 tree, which can be found at:
git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
trace-v6.19-rc4
Tag SHA1: 95c6df5f47e592a81fe0d78a16141b66158ca058
Head SHA1: 1e2ed4bfd50ace3c4272cfab7e9aa90956fb7ae0
Ben Dooks (1):
trace: ftrace_dump_on_oops[] is not exported, make it static
Julia Lawall (1):
tracing: Drop unneeded assignment to soft_mode
Steven Rostedt (2):
ftrace: Make ftrace_graph_ent depth field signed
tracing: Add recursion protection in kernel stack trace recording
Wupeng Ma (1):
ring-buffer: Avoid softlockup in ring_buffer_resize() during memory free
----
include/linux/ftrace.h | 2 +-
include/linux/trace_recursion.h | 9 +++++++++
kernel/trace/ring_buffer.c | 2 ++
kernel/trace/trace.c | 8 +++++++-
kernel/trace/trace_events.c | 7 +++----
5 files changed, 22 insertions(+), 6 deletions(-)
---------------------------
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 770f0dc993cc..a3a8989e3268 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -1167,7 +1167,7 @@ static inline void ftrace_init(void) { }
*/
struct ftrace_graph_ent {
unsigned long func; /* Current function */
- unsigned long depth;
+ long depth; /* signed to check for less than zero */
} __packed;
/*
diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h
index ae04054a1be3..e6ca052b2a85 100644
--- a/include/linux/trace_recursion.h
+++ b/include/linux/trace_recursion.h
@@ -34,6 +34,13 @@ enum {
TRACE_INTERNAL_SIRQ_BIT,
TRACE_INTERNAL_TRANSITION_BIT,
+ /* Internal event use recursion bits */
+ TRACE_INTERNAL_EVENT_BIT,
+ TRACE_INTERNAL_EVENT_NMI_BIT,
+ TRACE_INTERNAL_EVENT_IRQ_BIT,
+ TRACE_INTERNAL_EVENT_SIRQ_BIT,
+ TRACE_INTERNAL_EVENT_TRANSITION_BIT,
+
TRACE_BRANCH_BIT,
/*
* Abuse of the trace_recursion.
@@ -58,6 +65,8 @@ enum {
#define TRACE_LIST_START TRACE_INTERNAL_BIT
+#define TRACE_EVENT_START TRACE_INTERNAL_EVENT_BIT
+
#define TRACE_CONTEXT_MASK ((1 << (TRACE_LIST_START + TRACE_CONTEXT_BITS)) - 1)
/*
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 41c9f5d079be..630221b00838 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -3137,6 +3137,8 @@ int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
+
+ cond_resched();
}
}
out_err_unlock:
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 6f2148df14d9..baec63134ab6 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -138,7 +138,7 @@ cpumask_var_t __read_mostly tracing_buffer_mask;
* by commas.
*/
/* Set to string format zero to disable by default */
-char ftrace_dump_on_oops[MAX_TRACER_SIZE] = "0";
+static char ftrace_dump_on_oops[MAX_TRACER_SIZE] = "0";
/* When set, tracing will stop when a WARN*() is hit */
static int __disable_trace_on_warning;
@@ -3012,6 +3012,11 @@ static void __ftrace_trace_stack(struct trace_array *tr,
struct ftrace_stack *fstack;
struct stack_entry *entry;
int stackidx;
+ int bit;
+
+ bit = trace_test_and_set_recursion(_THIS_IP_, _RET_IP_, TRACE_EVENT_START);
+ if (bit < 0)
+ return;
/*
* Add one, for this function and the call to save_stack_trace()
@@ -3080,6 +3085,7 @@ static void __ftrace_trace_stack(struct trace_array *tr,
/* Again, don't let gcc optimize things here */
barrier();
__this_cpu_dec(ftrace_stack_reserve);
+ trace_clear_recursion(bit);
}
static inline void ftrace_trace_stack(struct trace_array *tr,
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 76067529db61..137b4d9bb116 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -826,16 +826,15 @@ static int __ftrace_event_enable_disable(struct trace_event_file *file,
* When soft_disable is set and enable is set, we want to
* register the tracepoint for the event, but leave the event
* as is. That means, if the event was already enabled, we do
- * nothing (but set soft_mode). If the event is disabled, we
- * set SOFT_DISABLED before enabling the event tracepoint, so
- * it still seems to be disabled.
+ * nothing. If the event is disabled, we set SOFT_DISABLED
+ * before enabling the event tracepoint, so it still seems
+ * to be disabled.
*/
if (!soft_disable)
clear_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags);
else {
if (atomic_inc_return(&file->sm_ref) > 1)
break;
- soft_mode = true;
/* Enable use of trace_buffered_event */
trace_buffered_event_enable();
}
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