Re: [Linux PPC] Disable PREEMPT
From: Shrikanth Hegde <sshegde@linux.ibm.com>
Date: 2026-09-18 09:27:09
Subsystem:
function hooks (ftrace), linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Steven Rostedt, Masami Hiramatsu, Madhavan Srinivasan, Linus Torvalds
Hi Michal. On 9/17/26 7:45 PM, Shrikanth Hegde wrote:
Hi Michal,quoted
quoted
Give it a try. I am suspecting both lockup, stack corruptions are secondary symptoms here. While recreate, I have different type of traces.Yes, it does work for the crash I see.Thanks. Give me sometime to see further on that. Didn't get any time today.
This is going to be the fix IMO. It passes all the recreates i have as of now. (Please ignore the whitespace mangling if any) Let me write changelog and send it across. ---
diff --git a/arch/powerpc/kernel/trace/ftrace_entry.S b/arch/powerpc/kernel/trace/ftrace_entry.S
index 6599fe3c6234..54c8727b48cd 100644
--- a/arch/powerpc/kernel/trace/ftrace_entry.S
+++ b/arch/powerpc/kernel/trace/ftrace_entry.S@@ -220,7 +220,9 @@ /* Restore gprs */ .if \allregs == 1 - REST_GPRS(2, 31, r1) + REST_GPRS(2, 12, r1) + /* Do not restore a stale PACA pointer if the task migrated */ + REST_GPRS(14, 31, r1) .else REST_GPRS(3, 10, r1) #if defined(CONFIG_LIVEPATCH_64) || defined(CONFIG_PPC_FTRACE_OUT_OF_LINE)