Revision 73863ab028579ed98c4f1f36d016536b1b415344 authored by Anton Vorontsov on 31 May 2012, 23:26:23 UTC, committed by Linus Torvalds on 01 June 2012, 00:49:29 UTC
Current CPU hotplug code has some task->mm handling issues: 1. Working with task->mm w/o getting mm or grabing the task lock is dangerous as ->mm might disappear (exit_mm() assigns NULL under task_lock(), so tasklist lock is not enough). We can't use get_task_mm()/mmput() pair as mmput() might sleep, so we must take the task lock while handle its mm. 2. Checking for process->mm is not enough because process' main thread may exit or detach its mm via use_mm(), but other threads may still have a valid mm. To fix this we would need to use find_lock_task_mm(), which would walk up all threads and returns an appropriate task (with task lock held). clear_tasks_mm_cpumask() has all the issues fixed, so let's use it. Suggested-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org> Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 3eaa73b
scan.c
/*
* Ultra Wide Band
* Scanning management
*
* Copyright (C) 2005-2006 Intel Corporation
* Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version
* 2 as published by the Free Software Foundation.
*
* 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. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*
*
*
* FIXME: docs
* FIXME: there are issues here on how BEACON and SCAN on USB RCI deal
* with each other. Currently seems that START_BEACON while
* SCAN_ONLY will cancel the scan, so we need to update the
* state here. Clarification request sent by email on
* 10/05/2005.
* 10/28/2005 No clear answer heard--maybe we'll hack the API
* so that when we start beaconing, if the HC is
* scanning in a mode not compatible with beaconing
* we just fail.
*/
#include <linux/device.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/stat.h>
#include "uwb-internal.h"
/**
* Start/stop scanning in a radio controller
*
* @rc: UWB Radio Controller
* @channel: Channel to scan; encodings in WUSB1.0[Table 5.12]
* @type: Type of scanning to do.
* @bpst_offset: value at which to start scanning (if type ==
* UWB_SCAN_ONLY_STARTTIME)
* @returns: 0 if ok, < 0 errno code on error
*
* We put the command on kmalloc'ed memory as some arches cannot do
* USB from the stack. The reply event is copied from an stage buffer,
* so it can be in the stack. See WUSB1.0[8.6.2.4] for more details.
*/
int uwb_rc_scan(struct uwb_rc *rc,
unsigned channel, enum uwb_scan_type type,
unsigned bpst_offset)
{
int result;
struct uwb_rc_cmd_scan *cmd;
struct uwb_rc_evt_confirm reply;
result = -ENOMEM;
cmd = kzalloc(sizeof(*cmd), GFP_KERNEL);
if (cmd == NULL)
goto error_kzalloc;
mutex_lock(&rc->uwb_dev.mutex);
cmd->rccb.bCommandType = UWB_RC_CET_GENERAL;
cmd->rccb.wCommand = cpu_to_le16(UWB_RC_CMD_SCAN);
cmd->bChannelNumber = channel;
cmd->bScanState = type;
cmd->wStartTime = cpu_to_le16(bpst_offset);
reply.rceb.bEventType = UWB_RC_CET_GENERAL;
reply.rceb.wEvent = UWB_RC_CMD_SCAN;
result = uwb_rc_cmd(rc, "SCAN", &cmd->rccb, sizeof(*cmd),
&reply.rceb, sizeof(reply));
if (result < 0)
goto error_cmd;
if (reply.bResultCode != UWB_RC_RES_SUCCESS) {
dev_err(&rc->uwb_dev.dev,
"SCAN: command execution failed: %s (%d)\n",
uwb_rc_strerror(reply.bResultCode), reply.bResultCode);
result = -EIO;
goto error_cmd;
}
rc->scanning = channel;
rc->scan_type = type;
error_cmd:
mutex_unlock(&rc->uwb_dev.mutex);
kfree(cmd);
error_kzalloc:
return result;
}
/*
* Print scanning state
*/
static ssize_t uwb_rc_scan_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct uwb_dev *uwb_dev = to_uwb_dev(dev);
struct uwb_rc *rc = uwb_dev->rc;
ssize_t result;
mutex_lock(&rc->uwb_dev.mutex);
result = sprintf(buf, "%d %d\n", rc->scanning, rc->scan_type);
mutex_unlock(&rc->uwb_dev.mutex);
return result;
}
/*
*
*/
static ssize_t uwb_rc_scan_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t size)
{
struct uwb_dev *uwb_dev = to_uwb_dev(dev);
struct uwb_rc *rc = uwb_dev->rc;
unsigned channel;
unsigned type;
unsigned bpst_offset = 0;
ssize_t result = -EINVAL;
result = sscanf(buf, "%u %u %u\n", &channel, &type, &bpst_offset);
if (result >= 2 && type < UWB_SCAN_TOP)
result = uwb_rc_scan(rc, channel, type, bpst_offset);
return result < 0 ? result : size;
}
/** Radio Control sysfs interface (declaration) */
DEVICE_ATTR(scan, S_IRUGO | S_IWUSR, uwb_rc_scan_show, uwb_rc_scan_store);
Computing file changes ...