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From:   Qi Zheng <zhengqi.arch@bytedance.com>
To:     peterz@infradead.org, keescook@chromium.org, jpoimboe@kernel.org,
        dave.hansen@linux.intel.com, bp@alien8.de, mingo@redhat.com,
        tglx@linutronix.de, rostedt@goodmis.org
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org,
        Qi Zheng <zhengqi.arch@bytedance.com>
Subject: [PATCH 2/2] x86: make __get_wchan() use arch_stack_walk()
Date:   Thu, 30 Mar 2023 16:15:52 +0800
Message-Id: <20230330081552.54178-3-zhengqi.arch@bytedance.com>
In-Reply-To: <20230330081552.54178-1-zhengqi.arch@bytedance.com>
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Make __get_wchan() use arch_stack_walk() directly to
avoid open-coding of unwind logic.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 arch/x86/kernel/process.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 3ab62ac98c2c..a6ff18fa6d5d 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -1000,6 +1000,17 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
 	return randomize_page(mm->brk, 0x02000000);
 }
 
+static bool get_wchan_cb(void *arg, unsigned long pc)
+{
+	unsigned long *addr = arg;
+
+	if (in_sched_functions(pc))
+		return true;
+
+	*addr = pc;
+	return false;
+}
+
 /*
  * Called from fs/proc with a reference on @p to find the function
  * which called into schedule(). This needs to be done carefully
@@ -1008,21 +1019,12 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
  */
 unsigned long __get_wchan(struct task_struct *p)
 {
-	struct unwind_state state;
 	unsigned long addr = 0;
 
 	if (!try_get_task_stack(p))
 		return 0;
 
-	for (unwind_start(&state, p, NULL, NULL); !unwind_done(&state);
-	     unwind_next_frame(&state)) {
-		addr = unwind_get_return_address(&state);
-		if (!addr)
-			break;
-		if (in_sched_functions(addr))
-			continue;
-		break;
-	}
+	arch_stack_walk(get_wchan_cb, &addr, p, NULL);
 
 	put_task_stack(p);
 
-- 
2.20.1