[PATCH v4 31/39] perf: Remove get_perf_callchain() 'init_nr' argument

Josh Poimboeuf
2025-01-22T02:32:24Z

The 'init_nr' argument has double duty: it's used to initialize both the
number of contexts and the number of stack entries. That's confusing
and the callers always pass zero anyway. Hard code the zero.

Acked-by: Namhyung Kim <Namhyung@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
include/linux/perf_event.h | 2 +-
kernel/bpf/stackmap.c | 4 ++--
kernel/events/callchain.c | 12 ++++++------
kernel/events/core.c | 2 +-
4 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index cb99ec8c9e96..4c8ff7258c6a 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1589,7 +1589,7 @@ DECLARE_PER_CPU(struct perf_callchain_entry, perf_callchain_entry);
extern void perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs);
extern void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs);
extern struct perf_callchain_entry *
-get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
+get_perf_callchain(struct pt_regs *regs, bool kernel, bool user,
u32 max_stack, bool crosstask, bool add_mark);
extern int get_callchain_buffers(int max_stack);
extern void put_callchain_buffers(void);
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 3615c06b7dfa..ec3a57a5fba1 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -314,7 +314,7 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
if (max_depth > sysctl_perf_event_max_stack)
max_depth = sysctl_perf_event_max_stack;

- trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
+ trace = get_perf_callchain(regs, kernel, user, max_depth,
false, false);

if (unlikely(!trace))
@@ -451,7 +451,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
else if (kernel && task)
trace = get_callchain_entry_for_task(task, max_depth);
else
- trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
+ trace = get_perf_callchain(regs, kernel, user, max_depth,
crosstask, false);

if (unlikely(!trace) || trace->nr < skip) {
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index 8a47e52a454f..83834203e144 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -216,7 +216,7 @@ static void fixup_uretprobe_trampoline_entries(struct perf_callchain_entry *entr
}

struct perf_callchain_entry *
-get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
+get_perf_callchain(struct pt_regs *regs, bool kernel, bool user,
u32 max_stack, bool crosstask, bool add_mark)
{
struct perf_callchain_entry *entry;
@@ -227,11 +227,11 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
if (!entry)
return NULL;

- ctx.entry = entry;
- ctx.max_stack = max_stack;
- ctx.nr = entry->nr = init_nr;
- ctx.contexts = 0;
- ctx.contexts_maxed = false;
+ ctx.entry = entry;
+ ctx.max_stack = max_stack;
+ ctx.nr = entry->nr = 0;
+ ctx.contexts = 0;
+ ctx.contexts_maxed = false;

if (kernel && !user_mode(regs)) {
if (add_mark)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 065f9188b44a..ebe457bacf96 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7801,7 +7801,7 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs)
if (!kernel && !user)
return &__empty_callchain;

- callchain = get_perf_callchain(regs, 0, kernel, user,
+ callchain = get_perf_callchain(regs, kernel, user,
max_stack, crosstask, true);
return callchain ?: &__empty_callchain;
}
--
2.48.1