On Sat, Mar 10, 2007 at 01:28:11AM +0900, Atsushi Nemoto wrote: > The save_fp_context()/restore_fp_context() might sleep on accessing > user stack and therefore might lose FPU ownership in middle of them. > Also we should not disable preempt around these functions. This patch > files this problem by allowing CpU exception in kernel partially. > > * Introduce TIF_ALLOW_FP_IN_KERNEL thread flag. If the flag was set, > CpU exception handler enables CU1 bit in interrupted kernel context > and returns without enabling interrupt (preempt) to make sure keep > FPU ownership until resume. > * Introduce enable_fp_in_kernel() and disable_fp_in_kernel(). While > we might lost FPU ownership in middle of CP0_STATUS manipulation > (for example local_irq_disable()), we can not assume CU1 bit always > reflects TIF_USEDFPU. Therefore enable_fp_in_kernel() must drop CU1 > bit if TIF_USEDFPU was cleared. > * The resume() function must drop CU1 bit in CP0_STATUS which are to > be saved. Applied as well. Thanks, Ralf
