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From 1cab5bd69eb1f995ced2d7576cb15f8a8941fd85 Mon Sep 17 00:00:00 2001
From: Tiezhu Yang <yangtiezhu@loongson.cn>
Date: Thu, 25 Nov 2021 19:39:32 +0800
Subject: [PATCH 1/1] MIPS: Fix using smp_processor_id() in preemptible in
show_cpuinfo()
There exists the following issue under DEBUG_PREEMPT:
BUG: using smp_processor_id() in preemptible [00000000] code: systemd/1
caller is show_cpuinfo+0x460/0xea0
...
Call Trace:
[<ffffffff8020f0dc>] show_stack+0x94/0x128
[<ffffffff80e6cab4>] dump_stack_lvl+0x94/0xd8
[<ffffffff80e74c5c>] check_preemption_disabled+0x104/0x110
[<ffffffff802209c8>] show_cpuinfo+0x460/0xea0
[<ffffffff80539d54>] seq_read_iter+0xfc/0x4f8
[<ffffffff804fcc10>] new_sync_read+0x110/0x1b8
[<ffffffff804ff57c>] vfs_read+0x1b4/0x1d0
[<ffffffff804ffb18>] ksys_read+0xd0/0x110
[<ffffffff8021c090>] syscall_common+0x34/0x58
We can see the following call trace:
show_cpuinfo()
cpu_has_fpu
current_cpu_data
smp_processor_id()
$ addr2line -f -e vmlinux 0xffffffff802209c8
show_cpuinfo
arch/mips/kernel/proc.c:188
$ head -188 arch/mips/kernel/proc.c | tail -1
if (cpu_has_fpu)
arch/mips/include/asm/cpu-features.h
# define cpu_has_fpu (current_cpu_data.options & MIPS_CPU_FPU)
arch/mips/include/asm/cpu-info.h
#define current_cpu_data cpu_data[smp_processor_id()]
Based on the above analysis, fix the issue by using raw_cpu_has_fpu
which calls raw_smp_processor_id() in show_cpuinfo().
Fixes: 626bfa037299 ("MIPS: kernel: proc: add CPU option reporting")
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
---
arch/mips/kernel/proc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/mips/kernel/proc.c
+++ b/arch/mips/kernel/proc.c
@@ -166,7 +166,7 @@ static int show_cpuinfo(struct seq_file
seq_puts(m, " tx39_cache");
if (cpu_has_octeon_cache)
seq_puts(m, " octeon_cache");
- if (cpu_has_fpu)
+ if (raw_cpu_has_fpu)
seq_puts(m, " fpu");
if (cpu_has_32fpr)
seq_puts(m, " 32fpr");
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