From 1cab5bd69eb1f995ced2d7576cb15f8a8941fd85 Mon Sep 17 00:00:00 2001 From: Tiezhu Yang 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: [] show_stack+0x94/0x128 [] dump_stack_lvl+0x94/0xd8 [] check_preemption_disabled+0x104/0x110 [] show_cpuinfo+0x460/0xea0 [] seq_read_iter+0xfc/0x4f8 [] new_sync_read+0x110/0x1b8 [] vfs_read+0x1b4/0x1d0 [] ksys_read+0xd0/0x110 [] 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 Signed-off-by: Thomas Bogendoerfer --- 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");