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Diffstat (limited to 'arch/ia64/include/asm/switch_to.h')
| -rw-r--r-- | arch/ia64/include/asm/switch_to.h | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/arch/ia64/include/asm/switch_to.h b/arch/ia64/include/asm/switch_to.h new file mode 100644 index 000000000..a5a4e0946 --- /dev/null +++ b/arch/ia64/include/asm/switch_to.h @@ -0,0 +1,71 @@ +/* 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); + +#define IA64_HAS_EXTRA_STATE(t) \ + ((t)->thread.flags & (IA64_THREAD_DBG_VALID|IA64_THREAD_PM_VALID)) + +#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 CONFIG_SMP +/* + * 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 */ |