Messages in this thread | | | Date | Tue, 29 Jul 2014 21:32:32 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH v4 2/5] x86,entry: Only call user_exit if TIF_NOHZ |
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On 07/28, Andy Lutomirski wrote: > > @@ -1449,7 +1449,12 @@ long syscall_trace_enter(struct pt_regs *regs) > { > long ret = 0; > > - user_exit(); > + /* > + * If TIF_NOHZ is set, we are required to call user_exit() before > + * doing anything that could touch RCU. > + */ > + if (test_thread_flag(TIF_NOHZ)) > + user_exit();
Personally I still think this change just adds more confusion, but I leave this to you and Frederic.
It is not that "If TIF_NOHZ is set, we are required to call user_exit()", we need to call user_exit() just because we enter the kernel. TIF_NOHZ is just the implementation detail which triggers this slow path.
At least it should be correct, unless I am confused even more than I think.
Oleg.
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