On Tue, Mar 24, 2015 at 03:21:33PM -0400, cmetc...@ezchip.com wrote:
> From: Chris Metcalf <cmetc...@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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