On December 22, 2015 10:02:12 AM PST, Mathieu Desnoyers
<mathieu.desnoy...@efficios.com> wrote:
>Wire up the thread local ABI on x86 32/64. Call the
>thread_local_abi_handle_notify_resume() function on return to
>userspace if TIF_NOTIFY_RESUME thread flag is set.
>
>This provides an ABI improving the speed of a getcpu operation
>on x86 by removing the need to perform a function call, "lsl"
>instruction, or system call on the fast path.
>
>Signed-off-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
>CC: Russell King <li...@arm.linux.org.uk>
>CC: Catalin Marinas <catalin.mari...@arm.com>
>CC: Will Deacon <will.dea...@arm.com>
>CC: Thomas Gleixner <t...@linutronix.de>
>CC: Paul Turner <p...@google.com>
>CC: Andrew Hunter <a...@google.com>
>CC: Peter Zijlstra <pet...@infradead.org>
>CC: Andy Lutomirski <l...@amacapital.net>
>CC: Andi Kleen <a...@firstfloor.org>
>CC: Dave Watson <davejwat...@fb.com>
>CC: Chris Lameter <c...@linux.com>
>CC: Ingo Molnar <mi...@redhat.com>
>CC: Ben Maurer <bmau...@fb.com>
>CC: Steven Rostedt <rost...@goodmis.org>
>CC: "Paul E. McKenney" <paul...@linux.vnet.ibm.com>
>CC: Josh Triplett <j...@joshtriplett.org>
>CC: Linus Torvalds <torva...@linux-foundation.org>
>CC: Andrew Morton <a...@linux-foundation.org>
>CC: Thomas Gleixner <t...@linutronix.de>
>CC: linux-...@vger.kernel.org
>---
> arch/x86/entry/common.c | 2 ++
> arch/x86/entry/syscalls/syscall_32.tbl | 1 +
> arch/x86/entry/syscalls/syscall_64.tbl | 1 +
> 3 files changed, 4 insertions(+)
>
>diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
>index a89fdbc..222cacf 100644
>--- a/arch/x86/entry/common.c
>+++ b/arch/x86/entry/common.c
>@@ -249,6 +249,8 @@ static void exit_to_usermode_loop(struct pt_regs
>*regs, u32 cached_flags)
> if (cached_flags & _TIF_NOTIFY_RESUME) {
> clear_thread_flag(TIF_NOTIFY_RESUME);
> tracehook_notify_resume(regs);
>+ if (thread_local_abi_active(current))
>+ thread_local_abi_handle_notify_resume(current);
Every caller seems likely to duplicate this pattern; why not make the call
itself a static inline containing this check and call (or no-op if compiled
out)?
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