From 4cda9ad55639841439f9993b4d69e0c551610274 Mon Sep 17 00:00:00 2001 From: Huacai Chen Date: Wed, 16 Jul 2014 09:19:16 +0800 Subject: MIPS: Remove BUG_ON(!is_fpu_owner()) in do_ade() commit 2e5767a27337812f6850b3fa362419e2f085e5c3 upstream. In do_ade(), is_fpu_owner() isn't preempt-safe. For example, when an unaligned ldc1 is executed, do_cpu() is called and then FPU will be enabled (and TIF_USEDFPU will be set for the current process). Then, do_ade() is called because the access is unaligned. If the current process is preempted at this time, TIF_USEDFPU will be cleard. So when the process is scheduled again, BUG_ON(!is_fpu_owner()) is triggered. This small program can trigger this BUG in a preemptible kernel: int main (int argc, char *argv[]) { double u64[2]; while (1) { asm volatile ( ".set push \n\t" ".set noreorder \n\t" "ldc1 $f3, 4(%0) \n\t" ".set pop \n\t" ::"r"(u64): ); } return 0; } V2: Remove the BUG_ON() unconditionally due to Paul's suggestion. Signed-off-by: Huacai Chen Signed-off-by: Jie Chen Signed-off-by: Rui Wang Cc: John Crispin Cc: Steven J. Hill Cc: linux-mips@linux-mips.org Cc: Fuxin Zhang Cc: Zhangjin Wu Signed-off-by: Ralf Baechle Signed-off-by: Greg Kroah-Hartman --- arch/mips/kernel/unaligned.c | 1 - 1 file changed, 1 deletion(-) (limited to 'arch/mips/kernel') diff --git a/arch/mips/kernel/unaligned.c b/arch/mips/kernel/unaligned.c index c369a5d35527..b897dde93e7a 100644 --- a/arch/mips/kernel/unaligned.c +++ b/arch/mips/kernel/unaligned.c @@ -605,7 +605,6 @@ static void emulate_load_store_insn(struct pt_regs *regs, case sdc1_op: die_if_kernel("Unaligned FP access in kernel code", regs); BUG_ON(!used_math()); - BUG_ON(!is_fpu_owner()); lose_fpu(1); /* Save FPU state for the emulator. */ res = fpu_emulator_cop1Handler(regs, ¤t->thread.fpu, 1, -- cgit v1.2.3