On Fri, Jul 06, 2012 at 02:00:18PM +0200, Frederic Weisbecker wrote:
> do_notify_resume() may be called on irq exit but it won't
> be protected between rcu_irq_enter() and rcu_irq_exit()
> and we don't call rcu_user_exit() on irq entry (unlike
> syscalls/exceptions entry).
>
> Since it can use RCU read side critical section, we must call
> rcu_user_exit() before doing anything there.
>
> This complete support for RCU userspace extended quiescent state
> in x86.
>
> Signed-off-by: Frederic Weisbecker <[email protected]>
> Cc: Alessio Igor Bogani <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Avi Kivity <[email protected]>
> Cc: Chris Metcalf <[email protected]>
> Cc: Christoph Lameter <[email protected]>
> Cc: Geoff Levand <[email protected]>
> Cc: Gilad Ben Yossef <[email protected]>
> Cc: Hakan Akkan <[email protected]>
> Cc: H. Peter Anvin <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Josh Triplett <[email protected]>
> Cc: Kevin Hilman <[email protected]>
> Cc: Max Krasnyansky <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Stephen Hemminger <[email protected]>
> Cc: Steven Rostedt <[email protected]>
> Cc: Sven-Thorsten Dietrich <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> ---
> arch/x86/Kconfig | 1 +
> arch/x86/kernel/signal.c | 2 ++
> 2 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index c70684f..38dfcc2 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -95,6 +95,7 @@ config X86
> select KTIME_SCALAR if X86_32
> select GENERIC_STRNCPY_FROM_USER
> select GENERIC_STRNLEN_USER
> + select HAVE_RCU_USER_QS if X86_64
And I will bite yet again. Why only 64-bit kernels?
Thanx, Paul
> config INSTRUCTION_DECODER
> def_bool (KPROBES || PERF_EVENTS || UPROBES)
> diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
> index 21af737..5af078e 100644
> --- a/arch/x86/kernel/signal.c
> +++ b/arch/x86/kernel/signal.c
> @@ -776,6 +776,8 @@ static void do_signal(struct pt_regs *regs)
> void
> do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
> {
> + rcu_user_exit();
> +
> #ifdef CONFIG_X86_MCE
> /* notify userspace of pending MCEs */
> if (thread_info_flags & _TIF_MCE_NOTIFY)
> --
> 1.7.5.4
>
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