C++ smp_wmb函数代码示例

static void __init wakeup_secondary(void)
{
	/*
	 * Write the address of secondary startup routine into the
	 * AuxCoreBoot1 where ROM code will jump and start executing
	 * on secondary core once out of WFE
	 * A barrier is added to ensure that write buffer is drained
	 */
	omap_auxcoreboot_addr(virt_to_phys(omap_secondary_startup));
	smp_wmb();

	/*
	 * Send a 'sev' to wake the secondary core from WFE.
	 * Drain the outstanding writes to memory
	 */
	dsb();
	set_event();
	mb();
}

/**
 * __bfq_exit_single_io_context - deassociate @cic from any running task.
 * @bfqd: bfq_data on which @cic is valid.
 * @cic: the cic being exited.
 *
 * Whenever no more tasks are using @cic or @bfqd is deallocated we
 * need to invalidate its entry in the radix tree hash table and to
 * release the queues it refers to.
 *
 * Called under the queue lock.
 */
static void __bfq_exit_single_io_context(struct bfq_data *bfqd,
					 struct cfq_io_context *cic)
{
	struct io_context *ioc = cic->ioc;

	list_del_init(&cic->queue_list);

	/*
	 * Make sure dead mark is seen for dead queues
	 */
	smp_wmb();
	rcu_assign_pointer(cic->key, bfqd_dead_key(bfqd));

	/*
	 * No write-side locking as no task is using @ioc (they're exited
	 * or bfqd is being deallocated.
	 */
	rcu_read_lock();
	if (rcu_dereference(ioc->ioc_data) == cic) {
		rcu_read_unlock();
		spin_lock(&ioc->lock);
		rcu_assign_pointer(ioc->ioc_data, NULL);
		spin_unlock(&ioc->lock);
	} else
		rcu_read_unlock();

	if (cic->cfqq[BLK_RW_ASYNC] != NULL) {
		bfq_exit_bfqq(bfqd, cic->cfqq[BLK_RW_ASYNC]);
		cic->cfqq[BLK_RW_ASYNC] = NULL;
	}

	if (cic->cfqq[BLK_RW_SYNC] != NULL) {
		/*
		 * If the bic is using a shared queue, put the reference
		 * taken on the io_context when the bic started using a
		 * shared bfq_queue.
		 */
		if (bfq_bfqq_coop(cic->cfqq[BLK_RW_SYNC]))
			put_io_context(ioc);
		bfq_exit_bfqq(bfqd, cic->cfqq[BLK_RW_SYNC]);
		cic->cfqq[BLK_RW_SYNC] = NULL;
	}
}

/*
 * This function implements a generic ability to update ruid, euid,
 * and suid.  This allows you to implement the 4.4 compatible seteuid().
 */
asmlinkage long sys_setresuid(uid_t ruid, uid_t euid, uid_t suid)
{
	int old_ruid = current->uid;
	int old_euid = current->euid;
	int old_suid = current->suid;
	int retval;

	retval = security_task_setuid(ruid, euid, suid, LSM_SETID_RES);
	if (retval)
		return retval;

	if (!capable(CAP_SETUID)) {
		if ((ruid != (uid_t) -1) && (ruid != current->uid) &&
		    (ruid != current->euid) && (ruid != current->suid))
			return -EPERM;
		if ((euid != (uid_t) -1) && (euid != current->uid) &&
		    (euid != current->euid) && (euid != current->suid))
			return -EPERM;
		if ((suid != (uid_t) -1) && (suid != current->uid) &&
		    (suid != current->euid) && (suid != current->suid))
			return -EPERM;
	}
	if (ruid != (uid_t) -1) {
		if (ruid != current->uid && set_user(ruid, euid != current->euid) < 0)
			return -EAGAIN;
	}
	if (euid != (uid_t) -1) {
		if (euid != current->euid) {
			set_dumpable(current->mm, suid_dumpable);
			smp_wmb();
		}
		current->euid = euid;
	}
	current->fsuid = current->euid;
	if (suid != (uid_t) -1)
		current->suid = suid;

	key_fsuid_changed(current);
	proc_id_connector(current, PROC_EVENT_UID);

	return security_task_post_setuid(old_ruid, old_euid, old_suid, LSM_SETID_RES);
}

/*
 * munging is applied to data by core as it passes between user
 * and kernel space
 */
static unsigned int comedi_buf_munge(struct comedi_async *async,
                                     unsigned int num_bytes)
{
    struct comedi_subdevice *s = async->subdevice;
    unsigned int count = 0;
    const unsigned num_sample_bytes = bytes_per_sample(s);

    if (!s->munge || (async->cmd.flags & CMDF_RAWDATA)) {
        async->munge_count += num_bytes;
        count = num_bytes;
    } else {
        /* don't munge partial samples */
        num_bytes -= num_bytes % num_sample_bytes;
        while (count < num_bytes) {
            int block_size = num_bytes - count;
            unsigned int buf_end;

            buf_end = async->prealloc_bufsz - async->munge_ptr;
            if (block_size > buf_end)
                block_size = buf_end;

            s->munge(s->device, s,
                     async->prealloc_buf + async->munge_ptr,
                     block_size, async->munge_chan);

            /*
             * ensure data is munged in buffer before the
             * async buffer munge_count is incremented
             */
            smp_wmb();

            async->munge_chan += block_size / num_sample_bytes;
            async->munge_chan %= async->cmd.chanlist_len;
            async->munge_count += block_size;
            async->munge_ptr += block_size;
            async->munge_ptr %= async->prealloc_bufsz;
            count += block_size;
        }
    }

    return count;
}

static int socfpga_boot_secondary(unsigned int cpu, struct task_struct *idle)
{
	int trampoline_size = &secondary_trampoline_end - &secondary_trampoline;

	if (cpu1start_addr) {
		memcpy(phys_to_virt(0), &secondary_trampoline, trampoline_size);

		__raw_writel(virt_to_phys(socfpga_secondary_startup),
			(sys_manager_base_addr + (cpu1start_addr & 0x000000ff)));

		flush_cache_all();
		smp_wmb();
		outer_clean_range(0, trampoline_size);

		/* This will release CPU #1 out of reset.*/
		__raw_writel(0, rst_manager_base_addr + 0x10);
	}

	return 0;
}

static int dtl_start(struct dtl *dtl)
{
	struct dtl_ring *dtlr = &per_cpu(dtl_rings, dtl->cpu);

	dtlr->buf = dtl->buf;
	dtlr->buf_end = dtl->buf + dtl->buf_entries;
	dtlr->write_index = 0;

	/* setting write_ptr enables logging into our buffer */
	smp_wmb();
	dtlr->write_ptr = dtl->buf;

	/* enable event logging */
	dtlr->saved_dtl_mask = lppaca[dtl->cpu].dtl_enable_mask;
	lppaca[dtl->cpu].dtl_enable_mask |= dtl_event_mask;

	dtl_consumer = consume_dtle;
	atomic_inc(&dtl_count);
	return 0;
}

static void chaos_read_callback(struct urb *urb)
{
	struct chaoskey *dev = urb->context;
	int status = urb->status;

	usb_dbg(dev->interface, "callback status (%d)", status);

	if (status == 0)
		dev->valid = urb->actual_length;
	else
		dev->valid = 0;

	dev->used = 0;

	/* must be seen first before validity is announced */
	smp_wmb();

	dev->reading = false;
	wake_up(&dev->wait_q);
}

static void __init wakeup_secondary(void)
{
#if defined(CHIPREG_BOOT_2ND_ADDR_OFFSET)
	void __iomem *chipRegBase;

	chipRegBase = IOMEM(KONA_CHIPREG_VA);

	writel((virt_to_phys(kona_secondary_startup) & (~0x3))|0x1, chipRegBase + CHIPREG_BOOT_2ND_ADDR_OFFSET);

	smp_wmb();

	/*
	 * Send a 'sev' to wake the secondary core from WFE.
	 * Drain the outstanding writes to memory
	 */
	dsb_sev();
	
	mb();
#endif
}

/*
 * This assumes that it can't be called concurrently with itself
 * but only with dequeue_ih_ring_entry.
 */
static bool
enqueue_ih_ring_entry(struct kfd_dev *kfd, const void *ih_ring_entry)
{
	unsigned int rptr = atomic_read(&kfd->interrupt_ring_rptr);
	unsigned int wptr = atomic_read(&kfd->interrupt_ring_wptr);

	if ((rptr - wptr) % kfd->interrupt_ring_size == kfd->device_info->ih_ring_entry_size) {
		/* This is very bad, the system is likely to hang. */
		dev_err_ratelimited(radeon_kfd_chardev(),
			"Interrupt ring overflow, dropping interrupt.\n");
		return false;
	}

	memcpy(kfd->interrupt_ring + wptr, ih_ring_entry, kfd->device_info->ih_ring_entry_size);
	wptr = (wptr + kfd->device_info->ih_ring_entry_size) % kfd->interrupt_ring_size;
	smp_wmb(); /* Ensure memcpy'd data is visible before wptr update. */
	atomic_set(&kfd->interrupt_ring_wptr, wptr);

	return true;
}

int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
{
	int err;
	unsigned long addr_wr = writable_address(bpt->bpt_addr);

	if (addr_wr == 0)
		return -1;

	err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
				BREAK_INSTR_SIZE);
	if (err)
		return err;

	err = probe_kernel_write((char *)addr_wr, arch_kgdb_ops.gdb_bpt_instr,
				 BREAK_INSTR_SIZE);
	smp_wmb();
	flush_icache_range((unsigned long)bpt->bpt_addr,
			   (unsigned long)bpt->bpt_addr + BREAK_INSTR_SIZE);
	return err;
}

static int __init vdso_init(void)
{
	int data_pages = sizeof(vdso_data_store) >> PAGE_SHIFT;

	/*
	 * We can disable vDSO support generally, but we need to retain
	 * one page to support the two-bundle (16-byte) rt_sigreturn path.
	 */
	if (!vdso_enabled) {
		size_t offset = (unsigned long)&__vdso_rt_sigreturn;
		static struct page *sigret_page;
		sigret_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
		BUG_ON(sigret_page == NULL);
		vdso_pagelist = &sigret_page;
		vdso_pages = 1;
		BUG_ON(offset >= PAGE_SIZE);
		memcpy(page_address(sigret_page) + offset,
		       vdso_start + offset, 16);
#ifdef CONFIG_COMPAT
		vdso32_pages = vdso_pages;
		vdso32_pagelist = vdso_pagelist;
#endif
		vdso_ready = 1;
		return 0;
	}

	vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
	vdso_pages += data_pages;
	vdso_pagelist = vdso_setup(vdso_start, vdso_pages);

#ifdef CONFIG_COMPAT
	vdso32_pages = (vdso32_end - vdso32_start) >> PAGE_SHIFT;
	vdso32_pages += data_pages;
	vdso32_pagelist = vdso_setup(vdso32_start, vdso32_pages);
#endif

	smp_wmb();
	vdso_ready = 1;

	return 0;
}

/**
 *  reuseport_add_sock - Add a socket to the reuseport group of another.
 *  @sk:  New socket to add to the group.
 *  @sk2: Socket belonging to the existing reuseport group.
 *  @bind_inany: Whether or not the group is bound to a local INANY address.
 *
 *  May return ENOMEM and not add socket to group under memory pressure.
 */
int reuseport_add_sock(struct sock *sk, struct sock *sk2, bool bind_inany)
{
	struct sock_reuseport *old_reuse, *reuse;

	if (!rcu_access_pointer(sk2->sk_reuseport_cb)) {
		int err = reuseport_alloc(sk2, bind_inany);

		if (err)
			return err;
	}

	spin_lock_bh(&reuseport_lock);
	reuse = rcu_dereference_protected(sk2->sk_reuseport_cb,
					  lockdep_is_held(&reuseport_lock));
	old_reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
					     lockdep_is_held(&reuseport_lock));
	if (old_reuse && old_reuse->num_socks != 1) {
		spin_unlock_bh(&reuseport_lock);
		return -EBUSY;
	}

	if (reuse->num_socks == reuse->max_socks) {
		reuse = reuseport_grow(reuse);
		if (!reuse) {
			spin_unlock_bh(&reuseport_lock);
			return -ENOMEM;
		}
	}

	reuse->socks[reuse->num_socks] = sk;
	/* paired with smp_rmb() in reuseport_select_sock() */
	smp_wmb();
	reuse->num_socks++;
	rcu_assign_pointer(sk->sk_reuseport_cb, reuse);

	spin_unlock_bh(&reuseport_lock);

	if (old_reuse)
		call_rcu(&old_reuse->rcu, reuseport_free_rcu);
	return 0;
}

int vlan_dev_set_egress_priority(const struct net_device *dev,
				 u32 skb_prio, u16 vlan_prio)
{
	struct vlan_dev_info *vlan = vlan_dev_info(dev);
	struct vlan_priority_tci_mapping *mp = NULL;
	struct vlan_priority_tci_mapping *np;
	u32 vlan_qos = (vlan_prio << VLAN_PRIO_SHIFT) & VLAN_PRIO_MASK;

	/* See if a priority mapping exists.. */
	mp = vlan->egress_priority_map[skb_prio & 0xF];
	while (mp) {
		if (mp->priority == skb_prio) {
			if (mp->vlan_qos && !vlan_qos)
				vlan->nr_egress_mappings--;
			else if (!mp->vlan_qos && vlan_qos)
				vlan->nr_egress_mappings++;
			mp->vlan_qos = vlan_qos;
			return 0;
		}
		mp = mp->next;
	}

	/* Create a new mapping then. */
	mp = vlan->egress_priority_map[skb_prio & 0xF];
	np = kmalloc(sizeof(struct vlan_priority_tci_mapping), GFP_KERNEL);
	if (!np)
		return -ENOBUFS;

	np->next = mp;
	np->priority = skb_prio;
	np->vlan_qos = vlan_qos;
	/* Before inserting this element in hash table, make sure all its fields
	 * are committed to memory.
	 * coupled with smp_rmb() in vlan_dev_get_egress_qos_mask()
	 */
	smp_wmb();
	vlan->egress_priority_map[skb_prio & 0xF] = np;
	if (vlan_qos)
		vlan->nr_egress_mappings++;
	return 0;
}

static int __rtas_suspend_last_cpu(struct rtas_suspend_me_data *data, int wake_when_done)
{
	u16 slb_size = mmu_slb_size;
	int rc = H_MULTI_THREADS_ACTIVE;
	int cpu;

	slb_set_size(SLB_MIN_SIZE);
	printk(KERN_DEBUG "calling ibm,suspend-me on cpu %i\n", smp_processor_id());

	while (rc == H_MULTI_THREADS_ACTIVE && !data->done) {
		rc = rtas_call(data->token, 0, 1, NULL);
		if (rc && rc != H_MULTI_THREADS_ACTIVE)
			printk(KERN_DEBUG "ibm,suspend-me returned %d\n", rc);
	}

	smp_rmb();
	if (rc || data->error)
		slb_set_size(slb_size);

	if (data->error)
		rc = data->error;

	data->error = rc;

	if (wake_when_done) {
		smp_wmb();
		data->done = 1;

		/* Ensure data->done is seen on all CPUs that are about to wake up
		 as a result of the H_PROD below */
		mb();

		for_each_online_cpu(cpu)
			plpar_hcall_norets(H_PROD, get_hard_smp_processor_id(cpu));
	}

	if (atomic_dec_return(&data->working) == 0)
		complete(data->complete);

	return rc;
}

static int
virtqueue_read_next_desc(VuDev *dev, struct vring_desc *desc,
                         int i, unsigned int max, unsigned int *next)
{
    /* If this descriptor says it doesn't chain, we're done. */
    if (!(desc[i].flags & VRING_DESC_F_NEXT)) {
        return VIRTQUEUE_READ_DESC_DONE;
    }

    /* Check they're not leading us off end of descriptors. */
    *next = desc[i].next;
    /* Make sure compiler knows to grab that: we don't want it changing! */
    smp_wmb();

    if (*next >= max) {
        vu_panic(dev, "Desc next is %u", next);
        return VIRTQUEUE_READ_DESC_ERROR;
    }

    return VIRTQUEUE_READ_DESC_MORE;
}