MIPS: Remove BUG_ON(!is_fpu_owner()) in do_ade()
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 <chenhc@lemote.com> Signed-off-by: Jie Chen <chenj@lemote.com> Signed-off-by: Rui Wang <wangr@lemote.com> Cc: <stable@vger.kernel.org> Cc: John Crispin <john@phrozen.org> Cc: Steven J. Hill <Steven.Hill@imgtec.com> Cc: linux-mips@linux-mips.org Cc: Fuxin Zhang <zhangfx@lemote.com> Cc: Zhangjin Wu <wuzhangjin@gmail.com> Cc: stable@vger.kernel.org Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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@ -690,7 +690,6 @@ static void emulate_load_store_insn(struct pt_regs *regs,
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case sdc1_op:
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die_if_kernel("Unaligned FP access in kernel code", regs);
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BUG_ON(!used_math());
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BUG_ON(!is_fpu_owner());
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lose_fpu(1); /* Save FPU state for the emulator. */
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res = fpu_emulator_cop1Handler(regs, ¤t->thread.fpu, 1,
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