/* SPDX-License-Identifier: GPL-2.0 */ /* * Low-level task switching. This is based on information published in * the Processor Abstraction Layer and the System Abstraction Layer * manual. * * Copyright (C) 1998-2003 Hewlett-Packard Co * David Mosberger-Tang <davidm@hpl.hp.com> * Copyright (C) 1999 Asit Mallick <asit.k.mallick@intel.com> * Copyright (C) 1999 Don Dugger <don.dugger@intel.com> */ #ifndef _ASM_IA64_SWITCH_TO_H #define _ASM_IA64_SWITCH_TO_H #include <linux/percpu.h> struct task_struct; /* * Context switch from one thread to another. If the two threads have * different address spaces, schedule() has already taken care of * switching to the new address space by calling switch_mm(). * * Disabling access to the fph partition and the debug-register * context switch MUST be done before calling ia64_switch_to() since a * newly created thread returns directly to * ia64_ret_from_syscall_clear_r8. */ extern struct task_struct *ia64_switch_to (void *next_task); extern void ia64_save_extra (struct task_struct *task); extern void ia64_load_extra (struct task_struct *task); #ifdef [31mCONFIG_PERFMON[0m DECLARE_PER_CPU(unsigned long, pfm_syst_info); # define PERFMON_IS_SYSWIDE() (__this_cpu_read(pfm_syst_info) & 0x1) #else # define PERFMON_IS_SYSWIDE() (0) #endif #define IA64_HAS_EXTRA_STATE(t) \ ((t)->thread.flags & (IA64_THREAD_DBG_VALID|IA64_THREAD_PM_VALID) \ || PERFMON_IS_SYSWIDE()) #define __switch_to(prev,next,last) do { \ if (IA64_HAS_EXTRA_STATE(prev)) \ ia64_save_extra(prev); \ if (IA64_HAS_EXTRA_STATE(next)) \ ia64_load_extra(next); \ ia64_psr(task_pt_regs(next))->dfh = !ia64_is_local_fpu_owner(next); \ (last) = ia64_switch_to((next)); \ } while (0) #ifdef [31mCONFIG_SMP[0m /* * In the SMP case, we save the fph state when context-switching away from a thread that * modified fph. This way, when the thread gets scheduled on another CPU, the CPU can * pick up the state from task->thread.fph, avoiding the complication of having to fetch * the latest fph state from another CPU. In other words: eager save, lazy restore. */ # define switch_to(prev,next,last) do { \ if (ia64_psr(task_pt_regs(prev))->mfh && ia64_is_local_fpu_owner(prev)) { \ ia64_psr(task_pt_regs(prev))->mfh = 0; \ (prev)->thread.flags |= IA64_THREAD_FPH_VALID; \ __ia64_save_fpu((prev)->thread.fph); \ } \ __switch_to(prev, next, last); \ /* "next" in old context is "current" in new context */ \ if (unlikely((current->thread.flags & IA64_THREAD_MIGRATION) && \ (task_cpu(current) != \ task_thread_info(current)->last_cpu))) { \ task_thread_info(current)->last_cpu = task_cpu(current); \ } \ } while (0) #else # define switch_to(prev,next,last) __switch_to(prev, next, last) #endif #endif /* _ASM_IA64_SWITCH_TO_H */ |