linux-kernel - Re: Regression bisected to f2f84b05e02b (bug: consolidate warn_slowpath

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Date: Tue, 21 May 2024 20:46:52 +0200
From: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To: mattst88@...il.com
Cc: keescook@...omium.org,
	linux-alpha@...r.kernel.org,
	linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Regression bisected to f2f84b05e02b (bug: consolidate warn_slowpath_fmt() usage)

Hi,

Replacing the calls to raw_smp_processor_id() in __warn() with just "0" fixes the problem for me:

diff --git a/kernel/panic.c b/kernel/panic.c
index 8bff183d6180..12f6cea6b8b0 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -671,11 +671,11 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
 
        if (file)
                pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n",
-                       raw_smp_processor_id(), current->pid, file, line,
+                       0, current->pid, file, line,
                        caller);
        else
                pr_warn("WARNING: CPU: %d PID: %d at %pS\n",
-                       raw_smp_processor_id(), current->pid, caller);
+                       0, current->pid, caller);
 
 #pragma GCC diagnostic push
 #ifndef __clang__

So, I assume the problem is that SMP support is not fully initialized at this
point yet such that raw_smp_processor_id() causes the zero pointer dereference.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
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