From 1a2a7f4ec8e3a7ac582dac4d01fcc7e8acd3bb30 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 6 Feb 2015 15:01:59 -0500 Subject: [PATCH] x86/fpu: Don't do __thread_fpu_end() if use_eager_fpu() unlazy_fpu()->__thread_fpu_end() doesn't look right if use_eager_fpu(). Unconditional __thread_fpu_end() is only correct if we know that this thread can't return to user-mode and use FPU. Fortunately it has only 2 callers. fpu_copy() checks use_eager_fpu(), and init_fpu(current) can be only called by the coredumping thread via regset->get(). But it is exported to modules, and imo this should be fixed anyway. And if we check use_eager_fpu() we can use __save_fpu() like fpu_copy() and save_init_fpu() do. - It seems that even !use_eager_fpu() case doesn't need the unconditional __thread_fpu_end(), we only need it if __save_init_fpu() returns 0. - It is still not clear to me if __save_init_fpu() can safely nest with another save + restore from __kernel_fpu_begin(). If not, we can use kernel_fpu_disable() to fix the race. Signed-off-by: Oleg Nesterov Signed-off-by: Rik van Riel Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1423252925-14451-3-git-send-email-riel@redhat.com Signed-off-by: Borislav Petkov --- Reading git-format-patch failed