Commit-ID: 4618e90965f272fe522f2af2523a60d0d4bc78f3 Gitweb: http://git.kernel.org/tip/4618e90965f272fe522f2af2523a60d0d4bc78f3 Author: Ingo Molnar <mi...@kernel.org> AuthorDate: Sat, 23 Sep 2017 15:00:10 +0200 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Tue, 26 Sep 2017 09:41:09 +0200
x86/fpu: Fix fpu__activate_fpstate_read() and update comments fpu__activate_fpstate_read() can be called for the current task when coredumping - or for stopped tasks when ptrace-ing. Implement this properly in the code and update the comments. This also fixes an incorrect (but harmless) warning introduced by one of the earlier patches. Cc: Andrew Morton <a...@linux-foundation.org> Cc: Andy Lutomirski <l...@amacapital.net> Cc: Borislav Petkov <b...@alien8.de> Cc: Dave Hansen <dave.han...@linux.intel.com> Cc: Eric Biggers <ebigge...@gmail.com> Cc: Fenghua Yu <fenghua...@intel.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Oleg Nesterov <o...@redhat.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Rik van Riel <r...@redhat.com> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Yu-cheng Yu <yu-cheng...@intel.com> Link: http://lkml.kernel.org/r/20170923130016.21448-28-mi...@kernel.org Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/kernel/fpu/core.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 93103a9..afd3f2a 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -254,18 +254,21 @@ EXPORT_SYMBOL_GPL(fpu__activate_curr); /* * This function must be called before we read a task's fpstate. * - * If the task has not used the FPU before then initialize its - * fpstate. + * There's two cases where this gets called: + * + * - for the current task (when coredumping), in which case we have + * to save the latest FPU registers into the fpstate, + * + * - or it's called for stopped tasks (ptrace), in which case the + * registers were already saved by the context-switch code when + * the task scheduled out - we only have to initialize the registers + * if they've never been initialized. * * If the task has used the FPU before then save it. */ void fpu__activate_fpstate_read(struct fpu *fpu) { - /* - * If fpregs are active (in the current CPU), then - * copy them to the fpstate: - */ - if (fpu->fpstate_active) { + if (fpu == ¤t->thread.fpu) { fpu__save(fpu); } else { if (!fpu->fpstate_active) {
