Merge branch 'for-4.7-dw' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/libata

[mirror_ubuntu-artful-kernel.git] / arch / tile / kernel / process.c

/*
 * Copyright 2010 Tilera Corporation. All Rights Reserved.
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 */

#include <linux/sched.h>
#include <linux/preempt.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/kprobes.h>
#include <linux/elfcore.h>
#include <linux/tick.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/compat.h>
#include <linux/hardirq.h>
#include <linux/syscalls.h>
#include <linux/kernel.h>
#include <linux/tracehook.h>
#include <linux/signal.h>
#include <linux/delay.h>
#include <linux/context_tracking.h>
#include <asm/stack.h>
#include <asm/switch_to.h>
#include <asm/homecache.h>
#include <asm/syscalls.h>
#include <asm/traps.h>
#include <asm/setup.h>
#include <asm/uaccess.h>
#ifdef CONFIG_HARDWALL
#include <asm/hardwall.h>
#endif
#include <arch/chip.h>
#include <arch/abi.h>
#include <arch/sim_def.h>

/*
 * Use the (x86) "idle=poll" option to prefer low latency when leaving the
 * idle loop over low power while in the idle loop, e.g. if we have
 * one thread per core and we want to get threads out of futex waits fast.
 */
static int __init idle_setup(char *str)
{
        if (!str)
                return -EINVAL;

        if (!strcmp(str, "poll")) {
                pr_info("using polling idle threads\n");
                cpu_idle_poll_ctrl(true);
                return 0;
        } else if (!strcmp(str, "halt")) {
                return 0;
        }
        return -1;
}
early_param("idle", idle_setup);

void arch_cpu_idle(void)
{
        __this_cpu_write(irq_stat.idle_timestamp, jiffies);
        _cpu_idle();
}

/*
 * Release a thread_info structure
 */
void arch_release_thread_info(struct thread_info *info)
{
        struct single_step_state *step_state = info->step_state;

        if (step_state) {

                /*
                 * FIXME: we don't munmap step_state->buffer
                 * because the mm_struct for this process (info->task->mm)
                 * has already been zeroed in exit_mm().  Keeping a
                 * reference to it here seems like a bad move, so this
                 * means we can't munmap() the buffer, and therefore if we
                 * ptrace multiple threads in a process, we will slowly
                 * leak user memory.  (Note that as soon as the last
                 * thread in a process dies, we will reclaim all user
                 * memory including single-step buffers in the usual way.)
                 * We should either assign a kernel VA to this buffer
                 * somehow, or we should associate the buffer(s) with the
                 * mm itself so we can clean them up that way.
                 */
                kfree(step_state);
        }
}

static void save_arch_state(struct thread_struct *t);

int copy_thread(unsigned long clone_flags, unsigned long sp,
                unsigned long arg, struct task_struct *p)
{
        struct pt_regs *childregs = task_pt_regs(p);
        unsigned long ksp;
        unsigned long *callee_regs;

        /*
         * Set up the stack and stack pointer appropriately for the
         * new child to find itself woken up in __switch_to().
         * The callee-saved registers must be on the stack to be read;
         * the new task will then jump to assembly support to handle
         * calling schedule_tail(), etc., and (for userspace tasks)
         * returning to the context set up in the pt_regs.
         */
        ksp = (unsigned long) childregs;
        ksp -= C_ABI_SAVE_AREA_SIZE;   /* interrupt-entry save area */
        ((long *)ksp)[0] = ((long *)ksp)[1] = 0;
        ksp -= CALLEE_SAVED_REGS_COUNT * sizeof(unsigned long);
        callee_regs = (unsigned long *)ksp;
        ksp -= C_ABI_SAVE_AREA_SIZE;   /* __switch_to() save area */
        ((long *)ksp)[0] = ((long *)ksp)[1] = 0;
        p->thread.ksp = ksp;

        /* Record the pid of the task that created this one. */
        p->thread.creator_pid = current->pid;

        if (unlikely(p->flags & PF_KTHREAD)) {
                /* kernel thread */
                memset(childregs, 0, sizeof(struct pt_regs));
                memset(&callee_regs[2], 0,
                       (CALLEE_SAVED_REGS_COUNT - 2) * sizeof(unsigned long));
                callee_regs[0] = sp;   /* r30 = function */
                callee_regs[1] = arg;  /* r31 = arg */
                p->thread.pc = (unsigned long) ret_from_kernel_thread;
                return 0;
        }

        /*
         * Start new thread in ret_from_fork so it schedules properly
         * and then return from interrupt like the parent.
         */
        p->thread.pc = (unsigned long) ret_from_fork;

        /*
         * Do not clone step state from the parent; each thread
         * must make its own lazily.
         */
        task_thread_info(p)->step_state = NULL;

#ifdef __tilegx__
        /*
         * Do not clone unalign jit fixup from the parent; each thread
         * must allocate its own on demand.
         */
        task_thread_info(p)->unalign_jit_base = NULL;
#endif

        /*
         * Copy the registers onto the kernel stack so the
         * return-from-interrupt code will reload it into registers.
         */
        *childregs = *current_pt_regs();
        childregs->regs[0] = 0;         /* return value is zero */
        if (sp)
                childregs->sp = sp;  /* override with new user stack pointer */
        memcpy(callee_regs, &childregs->regs[CALLEE_SAVED_FIRST_REG],
               CALLEE_SAVED_REGS_COUNT * sizeof(unsigned long));

        /* Save user stack top pointer so we can ID the stack vm area later. */
        p->thread.usp0 = childregs->sp;

        /*
         * If CLONE_SETTLS is set, set "tp" in the new task to "r4",
         * which is passed in as arg #5 to sys_clone().
         */
        if (clone_flags & CLONE_SETTLS)
                childregs->tp = childregs->regs[4];


#if CHIP_HAS_TILE_DMA()
        /*
         * No DMA in the new thread.  We model this on the fact that
         * fork() clears the pending signals, alarms, and aio for the child.
         */
        memset(&p->thread.tile_dma_state, 0, sizeof(struct tile_dma_state));
        memset(&p->thread.dma_async_tlb, 0, sizeof(struct async_tlb));
#endif

        /* New thread has its miscellaneous processor state bits clear. */
        p->thread.proc_status = 0;

#ifdef CONFIG_HARDWALL
        /* New thread does not own any networks. */
        memset(&p->thread.hardwall[0], 0,
               sizeof(struct hardwall_task) * HARDWALL_TYPES);
#endif


        /*
         * Start the new thread with the current architecture state
         * (user interrupt masks, etc.).
         */
        save_arch_state(&p->thread);

        return 0;
}

int set_unalign_ctl(struct task_struct *tsk, unsigned int val)
{
        task_thread_info(tsk)->align_ctl = val;
        return 0;
}

int get_unalign_ctl(struct task_struct *tsk, unsigned long adr)
{
        return put_user(task_thread_info(tsk)->align_ctl,
                        (unsigned int __user *)adr);
}

static struct task_struct corrupt_current = { .comm = "<corrupt>" };

/*
 * Return "current" if it looks plausible, or else a pointer to a dummy.
 * This can be helpful if we are just trying to emit a clean panic.
 */
struct task_struct *validate_current(void)
{
        struct task_struct *tsk = current;
        if (unlikely((unsigned long)tsk < PAGE_OFFSET ||
                     (high_memory && (void *)tsk > high_memory) ||
                     ((unsigned long)tsk & (__alignof__(*tsk) - 1)) != 0)) {
                pr_err("Corrupt 'current' %p (sp %#lx)\n", tsk, stack_pointer);
                tsk = &corrupt_current;
        }
        return tsk;
}

/* Take and return the pointer to the previous task, for schedule_tail(). */
struct task_struct *sim_notify_fork(struct task_struct *prev)
{
        struct task_struct *tsk = current;
        __insn_mtspr(SPR_SIM_CONTROL, SIM_CONTROL_OS_FORK_PARENT |
                     (tsk->thread.creator_pid << _SIM_CONTROL_OPERATOR_BITS));
        __insn_mtspr(SPR_SIM_CONTROL, SIM_CONTROL_OS_FORK |
                     (tsk->pid << _SIM_CONTROL_OPERATOR_BITS));
        return prev;
}

int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
{
        struct pt_regs *ptregs = task_pt_regs(tsk);
        elf_core_copy_regs(regs, ptregs);
        return 1;
}

#if CHIP_HAS_TILE_DMA()

/* Allow user processes to access the DMA SPRs */
void grant_dma_mpls(void)
{
#if CONFIG_KERNEL_PL == 2
        __insn_mtspr(SPR_MPL_DMA_CPL_SET_1, 1);
        __insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_1, 1);
#else
        __insn_mtspr(SPR_MPL_DMA_CPL_SET_0, 1);
        __insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_0, 1);
#endif
}

/* Forbid user processes from accessing the DMA SPRs */
void restrict_dma_mpls(void)
{
#if CONFIG_KERNEL_PL == 2
        __insn_mtspr(SPR_MPL_DMA_CPL_SET_2, 1);
        __insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_2, 1);
#else
        __insn_mtspr(SPR_MPL_DMA_CPL_SET_1, 1);
        __insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_1, 1);
#endif
}

/* Pause the DMA engine, then save off its state registers. */
static void save_tile_dma_state(struct tile_dma_state *dma)
{
        unsigned long state = __insn_mfspr(SPR_DMA_USER_STATUS);
        unsigned long post_suspend_state;

        /* If we're running, suspend the engine. */
        if ((state & DMA_STATUS_MASK) == SPR_DMA_STATUS__RUNNING_MASK)
                __insn_mtspr(SPR_DMA_CTR, SPR_DMA_CTR__SUSPEND_MASK);

        /*
         * Wait for the engine to idle, then save regs.  Note that we
         * want to record the "running" bit from before suspension,
         * and the "done" bit from after, so that we can properly
         * distinguish a case where the user suspended the engine from
         * the case where the kernel suspended as part of the context
         * swap.
         */
        do {
                post_suspend_state = __insn_mfspr(SPR_DMA_USER_STATUS);
        } while (post_suspend_state & SPR_DMA_STATUS__BUSY_MASK);

        dma->src = __insn_mfspr(SPR_DMA_SRC_ADDR);
        dma->src_chunk = __insn_mfspr(SPR_DMA_SRC_CHUNK_ADDR);
        dma->dest = __insn_mfspr(SPR_DMA_DST_ADDR);
        dma->dest_chunk = __insn_mfspr(SPR_DMA_DST_CHUNK_ADDR);
        dma->strides = __insn_mfspr(SPR_DMA_STRIDE);
        dma->chunk_size = __insn_mfspr(SPR_DMA_CHUNK_SIZE);
        dma->byte = __insn_mfspr(SPR_DMA_BYTE);
        dma->status = (state & SPR_DMA_STATUS__RUNNING_MASK) |
                (post_suspend_state & SPR_DMA_STATUS__DONE_MASK);
}

/* Restart a DMA that was running before we were context-switched out. */
static void restore_tile_dma_state(struct thread_struct *t)
{
        const struct tile_dma_state *dma = &t->tile_dma_state;

        /*
         * The only way to restore the done bit is to run a zero
         * length transaction.
         */
        if ((dma->status & SPR_DMA_STATUS__DONE_MASK) &&
            !(__insn_mfspr(SPR_DMA_USER_STATUS) & SPR_DMA_STATUS__DONE_MASK)) {
                __insn_mtspr(SPR_DMA_BYTE, 0);
                __insn_mtspr(SPR_DMA_CTR, SPR_DMA_CTR__REQUEST_MASK);
                while (__insn_mfspr(SPR_DMA_USER_STATUS) &
                       SPR_DMA_STATUS__BUSY_MASK)
                        ;
        }

        __insn_mtspr(SPR_DMA_SRC_ADDR, dma->src);
        __insn_mtspr(SPR_DMA_SRC_CHUNK_ADDR, dma->src_chunk);
        __insn_mtspr(SPR_DMA_DST_ADDR, dma->dest);
        __insn_mtspr(SPR_DMA_DST_CHUNK_ADDR, dma->dest_chunk);
        __insn_mtspr(SPR_DMA_STRIDE, dma->strides);
        __insn_mtspr(SPR_DMA_CHUNK_SIZE, dma->chunk_size);
        __insn_mtspr(SPR_DMA_BYTE, dma->byte);

        /*
         * Restart the engine if we were running and not done.
         * Clear a pending async DMA fault that we were waiting on return
         * to user space to execute, since we expect the DMA engine
         * to regenerate those faults for us now.  Note that we don't
         * try to clear the TIF_ASYNC_TLB flag, since it's relatively
         * harmless if set, and it covers both DMA and the SN processor.
         */
        if ((dma->status & DMA_STATUS_MASK) == SPR_DMA_STATUS__RUNNING_MASK) {
                t->dma_async_tlb.fault_num = 0;
                __insn_mtspr(SPR_DMA_CTR, SPR_DMA_CTR__REQUEST_MASK);
        }
}

#endif

static void save_arch_state(struct thread_struct *t)
{
#if CHIP_HAS_SPLIT_INTR_MASK()
        t->interrupt_mask = __insn_mfspr(SPR_INTERRUPT_MASK_0_0) |
                ((u64)__insn_mfspr(SPR_INTERRUPT_MASK_0_1) << 32);
#else
        t->interrupt_mask = __insn_mfspr(SPR_INTERRUPT_MASK_0);
#endif
        t->ex_context[0] = __insn_mfspr(SPR_EX_CONTEXT_0_0);
        t->ex_context[1] = __insn_mfspr(SPR_EX_CONTEXT_0_1);
        t->system_save[0] = __insn_mfspr(SPR_SYSTEM_SAVE_0_0);
        t->system_save[1] = __insn_mfspr(SPR_SYSTEM_SAVE_0_1);
        t->system_save[2] = __insn_mfspr(SPR_SYSTEM_SAVE_0_2);
        t->system_save[3] = __insn_mfspr(SPR_SYSTEM_SAVE_0_3);
        t->intctrl_0 = __insn_mfspr(SPR_INTCTRL_0_STATUS);
        t->proc_status = __insn_mfspr(SPR_PROC_STATUS);
#if !CHIP_HAS_FIXED_INTVEC_BASE()
        t->interrupt_vector_base = __insn_mfspr(SPR_INTERRUPT_VECTOR_BASE_0);
#endif
        t->tile_rtf_hwm = __insn_mfspr(SPR_TILE_RTF_HWM);
#if CHIP_HAS_DSTREAM_PF()
        t->dstream_pf = __insn_mfspr(SPR_DSTREAM_PF);
#endif
}

static void restore_arch_state(const struct thread_struct *t)
{
#if CHIP_HAS_SPLIT_INTR_MASK()
        __insn_mtspr(SPR_INTERRUPT_MASK_0_0, (u32) t->interrupt_mask);
        __insn_mtspr(SPR_INTERRUPT_MASK_0_1, t->interrupt_mask >> 32);
#else
        __insn_mtspr(SPR_INTERRUPT_MASK_0, t->interrupt_mask);
#endif
        __insn_mtspr(SPR_EX_CONTEXT_0_0, t->ex_context[0]);
        __insn_mtspr(SPR_EX_CONTEXT_0_1, t->ex_context[1]);
        __insn_mtspr(SPR_SYSTEM_SAVE_0_0, t->system_save[0]);
        __insn_mtspr(SPR_SYSTEM_SAVE_0_1, t->system_save[1]);
        __insn_mtspr(SPR_SYSTEM_SAVE_0_2, t->system_save[2]);
        __insn_mtspr(SPR_SYSTEM_SAVE_0_3, t->system_save[3]);
        __insn_mtspr(SPR_INTCTRL_0_STATUS, t->intctrl_0);
        __insn_mtspr(SPR_PROC_STATUS, t->proc_status);
#if !CHIP_HAS_FIXED_INTVEC_BASE()
        __insn_mtspr(SPR_INTERRUPT_VECTOR_BASE_0, t->interrupt_vector_base);
#endif
        __insn_mtspr(SPR_TILE_RTF_HWM, t->tile_rtf_hwm);
#if CHIP_HAS_DSTREAM_PF()
        __insn_mtspr(SPR_DSTREAM_PF, t->dstream_pf);
#endif
}


void _prepare_arch_switch(struct task_struct *next)
{
#if CHIP_HAS_TILE_DMA()
        struct tile_dma_state *dma = &current->thread.tile_dma_state;
        if (dma->enabled)
                save_tile_dma_state(dma);
#endif
}


struct task_struct *__sched _switch_to(struct task_struct *prev,
                                       struct task_struct *next)
{
        /* DMA state is already saved; save off other arch state. */
        save_arch_state(&prev->thread);

#if CHIP_HAS_TILE_DMA()
        /*
         * Restore DMA in new task if desired.
         * Note that it is only safe to restart here since interrupts
         * are disabled, so we can't take any DMATLB miss or access
         * interrupts before we have finished switching stacks.
         */
        if (next->thread.tile_dma_state.enabled) {
                restore_tile_dma_state(&next->thread);
                grant_dma_mpls();
        } else {
                restrict_dma_mpls();
        }
#endif

        /* Restore other arch state. */
        restore_arch_state(&next->thread);

#ifdef CONFIG_HARDWALL
        /* Enable or disable access to the network registers appropriately. */
        hardwall_switch_tasks(prev, next);
#endif

        /* Notify the simulator of task exit. */
        if (unlikely(prev->state == TASK_DEAD))
                __insn_mtspr(SPR_SIM_CONTROL, SIM_CONTROL_OS_EXIT |
                             (prev->pid << _SIM_CONTROL_OPERATOR_BITS));

        /*
         * Switch kernel SP, PC, and callee-saved registers.
         * In the context of the new task, return the old task pointer
         * (i.e. the task that actually called __switch_to).
         * Pass the value to use for SYSTEM_SAVE_K_0 when we reset our sp.
         */
        return __switch_to(prev, next, next_current_ksp0(next));
}

/*
 * This routine is called on return from interrupt if any of the
 * TIF_ALLWORK_MASK flags are set in thread_info->flags.  It is
 * entered with interrupts disabled so we don't miss an event that
 * modified the thread_info flags.  We loop until all the tested flags
 * are clear.  Note that the function is called on certain conditions
 * that are not listed in the loop condition here (e.g. SINGLESTEP)
 * which guarantees we will do those things once, and redo them if any
 * of the other work items is re-done, but won't continue looping if
 * all the other work is done.
 */
void prepare_exit_to_usermode(struct pt_regs *regs, u32 thread_info_flags)
{
        if (WARN_ON(!user_mode(regs)))
                return;

        do {
                local_irq_enable();

                if (thread_info_flags & _TIF_NEED_RESCHED)
                        schedule();

#if CHIP_HAS_TILE_DMA()
                if (thread_info_flags & _TIF_ASYNC_TLB)
                        do_async_page_fault(regs);
#endif

                if (thread_info_flags & _TIF_SIGPENDING)
                        do_signal(regs);

                if (thread_info_flags & _TIF_NOTIFY_RESUME) {
                        clear_thread_flag(TIF_NOTIFY_RESUME);
                        tracehook_notify_resume(regs);
                }

                local_irq_disable();
                thread_info_flags = READ_ONCE(current_thread_info()->flags);

        } while (thread_info_flags & _TIF_WORK_MASK);

        if (thread_info_flags & _TIF_SINGLESTEP) {
                single_step_once(regs);
#ifndef __tilegx__
                /*
                 * FIXME: on tilepro, since we enable interrupts in
                 * this routine, it's possible that we miss a signal
                 * or other asynchronous event.
                 */
                local_irq_disable();
#endif
        }

        user_enter();
}

unsigned long get_wchan(struct task_struct *p)
{
        struct KBacktraceIterator kbt;

        if (!p || p == current || p->state == TASK_RUNNING)
                return 0;

        for (KBacktraceIterator_init(&kbt, p, NULL);
             !KBacktraceIterator_end(&kbt);
             KBacktraceIterator_next(&kbt)) {
                if (!in_sched_functions(kbt.it.pc))
                        return kbt.it.pc;
        }

        return 0;
}

/* Flush thread state. */
void flush_thread(void)
{
        /* Nothing */
}

/*
 * Free current thread data structures etc..
 */
void exit_thread(struct task_struct *tsk)
{
#ifdef CONFIG_HARDWALL
        /*
         * Remove the task from the list of tasks that are associated
         * with any live hardwalls.  (If the task that is exiting held
         * the last reference to a hardwall fd, it would already have
         * been released and deactivated at this point.)
         */
        hardwall_deactivate_all(tsk);
#endif
}

void tile_show_regs(struct pt_regs *regs)
{
        int i;
#ifdef __tilegx__
        for (i = 0; i < 17; i++)
                pr_err(" r%-2d: "REGFMT" r%-2d: "REGFMT" r%-2d: "REGFMT"\n",
                       i, regs->regs[i], i+18, regs->regs[i+18],
                       i+36, regs->regs[i+36]);
        pr_err(" r17: "REGFMT" r35: "REGFMT" tp : "REGFMT"\n",
               regs->regs[17], regs->regs[35], regs->tp);
        pr_err(" sp : "REGFMT" lr : "REGFMT"\n", regs->sp, regs->lr);
#else
        for (i = 0; i < 13; i++)
                pr_err(" r%-2d: "REGFMT" r%-2d: "REGFMT
                       " r%-2d: "REGFMT" r%-2d: "REGFMT"\n",
                       i, regs->regs[i], i+14, regs->regs[i+14],
                       i+27, regs->regs[i+27], i+40, regs->regs[i+40]);
        pr_err(" r13: "REGFMT" tp : "REGFMT" sp : "REGFMT" lr : "REGFMT"\n",
               regs->regs[13], regs->tp, regs->sp, regs->lr);
#endif
        pr_err(" pc : "REGFMT" ex1: %ld     faultnum: %ld flags:%s%s%s%s\n",
               regs->pc, regs->ex1, regs->faultnum,
               is_compat_task() ? " compat" : "",
               (regs->flags & PT_FLAGS_DISABLE_IRQ) ? " noirq" : "",
               !(regs->flags & PT_FLAGS_CALLER_SAVES) ? " nocallersave" : "",
               (regs->flags & PT_FLAGS_RESTORE_REGS) ? " restoreregs" : "");
}

void show_regs(struct pt_regs *regs)
{
        struct KBacktraceIterator kbt;

        show_regs_print_info(KERN_DEFAULT);
        tile_show_regs(regs);

        KBacktraceIterator_init(&kbt, NULL, regs);
        tile_show_stack(&kbt);
}

/* To ensure stack dump on tiles occurs one by one. */
static DEFINE_SPINLOCK(backtrace_lock);
/* To ensure no backtrace occurs before all of the stack dump are done. */
static atomic_t backtrace_cpus;
/* The cpu mask to avoid reentrance. */
static struct cpumask backtrace_mask;

void do_nmi_dump_stack(struct pt_regs *regs)
{
        int is_idle = is_idle_task(current) && !in_interrupt();
        int cpu;

        nmi_enter();
        cpu = smp_processor_id();
        if (WARN_ON_ONCE(!cpumask_test_and_clear_cpu(cpu, &backtrace_mask)))
                goto done;

        spin_lock(&backtrace_lock);
        if (is_idle)
                pr_info("CPU: %d idle\n", cpu);
        else
                show_regs(regs);
        spin_unlock(&backtrace_lock);
        atomic_dec(&backtrace_cpus);
done:
        nmi_exit();
}

#ifdef __tilegx__
void arch_trigger_all_cpu_backtrace(bool self)
{
        struct cpumask mask;
        HV_Coord tile;
        unsigned int timeout;
        int cpu;
        int ongoing;
        HV_NMI_Info info[NR_CPUS];

        ongoing = atomic_cmpxchg(&backtrace_cpus, 0, num_online_cpus() - 1);
        if (ongoing != 0) {
                pr_err("Trying to do all-cpu backtrace.\n");
                pr_err("But another all-cpu backtrace is ongoing (%d cpus left)\n",
                       ongoing);
                if (self) {
                        pr_err("Reporting the stack on this cpu only.\n");
                        dump_stack();
                }
                return;
        }

        cpumask_copy(&mask, cpu_online_mask);
        cpumask_clear_cpu(smp_processor_id(), &mask);
        cpumask_copy(&backtrace_mask, &mask);

        /* Backtrace for myself first. */
        if (self)
                dump_stack();

        /* Tentatively dump stack on remote tiles via NMI. */
        timeout = 100;
        while (!cpumask_empty(&mask) && timeout) {
                for_each_cpu(cpu, &mask) {
                        tile.x = cpu_x(cpu);
                        tile.y = cpu_y(cpu);
                        info[cpu] = hv_send_nmi(tile, TILE_NMI_DUMP_STACK, 0);
                        if (info[cpu].result == HV_NMI_RESULT_OK)
                                cpumask_clear_cpu(cpu, &mask);
                }

                mdelay(10);
                timeout--;
        }

        /* Warn about cpus stuck in ICS and decrement their counts here. */
        if (!cpumask_empty(&mask)) {
                for_each_cpu(cpu, &mask) {
                        switch (info[cpu].result) {
                        case HV_NMI_RESULT_FAIL_ICS:
                                pr_warn("Skipping stack dump of cpu %d in ICS at pc %#llx\n",
                                        cpu, info[cpu].pc);
                                break;
                        case HV_NMI_RESULT_FAIL_HV:
                                pr_warn("Skipping stack dump of cpu %d in hypervisor\n",
                                        cpu);
                                break;
                        case HV_ENOSYS:
                                pr_warn("Hypervisor too old to allow remote stack dumps.\n");
                                goto skip_for_each;
                        default:  /* should not happen */
                                pr_warn("Skipping stack dump of cpu %d [%d,%#llx]\n",
                                        cpu, info[cpu].result, info[cpu].pc);
                                break;
                        }
                }
skip_for_each:
                atomic_sub(cpumask_weight(&mask), &backtrace_cpus);
        }
}
#endif /* __tilegx_ */