Messages in this thread Patch in this message | | | Date | Tue, 2 Sep 2014 19:57:27 +0200 | From | Oleg Nesterov <> | Subject | [PATCH v2 5/7] x86, fpu: copy_process: sanitize fpu->last_cpu initialization |
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Cosmetic, but imho memset(&dst->thread.fpu, 0) is not good simply because it hides the (important) usage of ->has_fpu/etc from grep. Change this code to initialize the members explicitly.
And note that ->last_cpu = 0 looks simply wrong, this can confuse fpu_lazy_restore() if per_cpu(fpu_owner_task, 0) has already exited and copy_process() re-allocated the same task_struct. Fortunately this is not actually possible because child->fpu_counter == 0 and thus fpu_lazy_restore() will not be called, but still this is not clean/robust.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Suresh Siddha <sbsiddha@gmail.com> --- arch/x86/kernel/process.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 1dfdd69..9b9f088 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -66,7 +66,9 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) { *dst = *src; - memset(&dst->thread.fpu, 0, sizeof(dst->thread.fpu)); + dst->thread.fpu.has_fpu = 0; + dst->thread.fpu.last_cpu = ~0; + dst->thread.fpu.state = NULL; if (tsk_used_math(src)) { int err = fpu_alloc(&dst->thread.fpu); if (err) -- 1.5.5.1
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