Messages in this thread | | | Date | Tue, 24 Mar 2015 22:15:17 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 2/4] tile: support CONTEXT_TRACKING and thus NOHZ_FULL |
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On Tue, Mar 24, 2015 at 03:21:33PM -0400, cmetcalf@ezchip.com wrote: > From: Chris Metcalf <cmetcalf@ezchip.com> > > Add the TIF_NOHZ flag appropriately. > > Add call to user_exit() on entry to do_work_pending() and on entry > to syscalls via do_syscall_trace_enter(), and also the top of > do_syscall_trace_exit() just because it's done in x86.
You only need to protect do_syscall_trace_exit() if there is a risk that something calls user_enter() before. x86 does it so because schedule_user() can be called before although I think we've changed schedule_user() to use exception_enter/exit. I should check if that user_exit() in do_syscall_trace_exit() is still necessary in x86.
Anyway, calling user_exit() on context tracking kerne mode doesn't do any harm.
> diff --git a/arch/tile/kernel/process.c b/arch/tile/kernel/process.c > index 48e5773dd0b7..b403c2e3e263 100644 > --- a/arch/tile/kernel/process.c > +++ b/arch/tile/kernel/process.c > @@ -27,6 +27,7 @@ > #include <linux/kernel.h> > #include <linux/tracehook.h> > #include <linux/signal.h> > +#include <linux/context_tracking.h> > #include <asm/stack.h> > #include <asm/switch_to.h> > #include <asm/homecache.h> > @@ -474,6 +475,8 @@ int do_work_pending(struct pt_regs *regs, u32 thread_info_flags) > if (!user_mode(regs)) > return 0; > > + user_exit(); > + > /* Enable interrupts; they are disabled again on return to caller. */ > local_irq_enable(); > > @@ -496,11 +499,12 @@ int do_work_pending(struct pt_regs *regs, u32 thread_info_flags) > tracehook_notify_resume(regs); > return 1; > } > - if (thread_info_flags & _TIF_SINGLESTEP) { > + if (thread_info_flags & _TIF_SINGLESTEP) > single_step_once(regs); > - return 0; > - } > - panic("work_pending: bad flags %#x\n", thread_info_flags); > + > + user_enter();
So, do work pending is called from syscall exit only? Or does it concern interrupts, exceptions as well?
Well if it's always followed by a return to userspace, it should be fine.
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