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 <[email protected]>
Signed-off-by: Jie Chen <[email protected]>
Signed-off-by: Rui Wang <[email protected]>
Cc: <[email protected]>
Cc: John Crispin <[email protected]>
Cc: Steven J. Hill <[email protected]>
Cc: [email protected]
Cc: Fuxin Zhang <[email protected]>
Cc: Zhangjin Wu <[email protected]>
Cc: [email protected]
Signed-off-by: Ralf Baechle <[email protected]>

0 files changed, 0 insertions, 0 deletions