From d3a4f48d4866b8623ca9adde8ce4e5fde979c132 Mon Sep 17 00:00:00 2001 From: Stephane Eranian Date: Tue, 26 Sep 2006 10:52:28 +0200 Subject: [PATCH] x86-64 TIF flags for debug regs and io bitmap in ctxsw Hello, Following my discussion with Andi. Here is a patch that introduces two new TIF flags to simplify the context switch code in __switch_to(). The idea is to minimize the number of cache lines accessed in the common case, i.e., when neither the debug registers nor the I/O bitmap are used. This patch covers the x86-64 modifications. A patch for i386 follows. Changelog: - add TIF_DEBUG to track when debug registers are active - add TIF_IO_BITMAP to track when I/O bitmap is used - modify __switch_to() to use the new TIF flags : eranian@hpl.hp.com Signed-off-by: Andi Kleen --- arch/x86_64/kernel/ptrace.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'arch/x86_64/kernel/ptrace.c') diff --git a/arch/x86_64/kernel/ptrace.c b/arch/x86_64/kernel/ptrace.c index 2d50024c9f3..d35ec1bc696 100644 --- a/arch/x86_64/kernel/ptrace.c +++ b/arch/x86_64/kernel/ptrace.c @@ -420,9 +420,13 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data) if ((0x5554 >> ((data >> (16 + 4*i)) & 0xf)) & 1) break; if (i == 4) { - child->thread.debugreg7 = data; + child->thread.debugreg7 = data; + if (data) + set_tsk_thread_flag(child, TIF_DEBUG); + else + clear_tsk_thread_flag(child, TIF_DEBUG); ret = 0; - } + } break; } break; -- cgit v1.2.3