On 01/15, Oleg Nesterov wrote: > > Let me send initial kernel_fpu_begin/end cleanups, I believe they make > sense anyway and won't conflict with your changes. > > This is actually resend, I sent more patches some time ago but they were > ignored. > > Note that (I hope) we can do more changes on top of this series, in > particular: > > - remove all checks from irq_fpu_usable() except in_kernel_fpu > > - do not abuse FPU in kernel threads, this makes sense even if > use_eager_fpu(), and with or without the changes you proposed.
On top of this series. Initially I was going to make more changes, but then I decided to delay the cleanups. IMHO this code needs them in any case. math_state_restore() and its usage doesn't look nice. init_fpu() too, and unlazy_fpu(current) is simply wrong afaics. Fortunately the only caller of init_fpu(current) is coredump, so this task can't return to user-mode, still this doesn't look good. And it should be unified with save_init_fpu(). Which has the wrong WARN_ON_ONCE(!__thread_has_fpu(tsk)). And I am not sure that unlazy_fpu() is correct wrt __kernel_fpu_begin(), but probably this is because I do not know how fpu works. If the nested __save_init_fpu() is fine, then why (before the previous changes) __kernel_fpu_begin() does __thread_clear_has_fpu() first? Rik, to remind, I think that your changes need 1 + 2 at least, to avoid the performance regression. Perhaps this needs a single patch. 3/3 is not strictly neccessary, but imo it makes sense anyway, even without your changes. And if we add TIF_LOAD_FPU, it would be nice to filter out kthreads automatically. Could someone review this series? If this makes any sense, I'll try to make the cleanups later. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
