Messages in this thread | | | Subject | Re: [RFC PATCH v2 2/3] thread_local_abi: wire up x86 32/64 system call | From | Josh Triplett <> | Date | Wed, 23 Dec 2015 19:42:14 -0800 |
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On December 22, 2015 10:02:12 AM PST, Mathieu Desnoyers <mathieu.desnoyers@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.desnoyers@efficios.com> >CC: Russell King <linux@arm.linux.org.uk> >CC: Catalin Marinas <catalin.marinas@arm.com> >CC: Will Deacon <will.deacon@arm.com> >CC: Thomas Gleixner <tglx@linutronix.de> >CC: Paul Turner <pjt@google.com> >CC: Andrew Hunter <ahh@google.com> >CC: Peter Zijlstra <peterz@infradead.org> >CC: Andy Lutomirski <luto@amacapital.net> >CC: Andi Kleen <andi@firstfloor.org> >CC: Dave Watson <davejwatson@fb.com> >CC: Chris Lameter <cl@linux.com> >CC: Ingo Molnar <mingo@redhat.com> >CC: Ben Maurer <bmaurer@fb.com> >CC: Steven Rostedt <rostedt@goodmis.org> >CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> >CC: Josh Triplett <josh@joshtriplett.org> >CC: Linus Torvalds <torvalds@linux-foundation.org> >CC: Andrew Morton <akpm@linux-foundation.org> >CC: Thomas Gleixner <tglx@linutronix.de> >CC: linux-api@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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