This patch will enable Per-port event feature defined in EHCI 1.1
addendum. This feature addresses an issue where HCD is currently
required to read and parse PORTSC for all enabled root hub ports. With
this patch, the overhead will be reduced.
Signed-off-by: NAlek Du <alek.du@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

With this patch, the LPM capable EHCI host controller can put device
into L1 sleep state which is a mode that can enter/exit quickly, and
reduce power consumption.
Signed-off-by: NJacob Pan <jacob.jun.pan@intel.com>
Signed-off-by: NAlek Du <alek.du@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

EHCI 1.1 addendum introduced several energy efficiency extensions for
EHCI USB host controllers:
1. LPM (link power management)
2. Per-port change
3. Shorter periodic frame list
4. Hardware prefetching

This patch is intended to define the HW bits and debug interface for
EHCI 1.1 addendum. The LPM and Per-port change patches will be sent out
after this patch.
Signed-off-by: NJacob Pan <jacob.jun.pan@intel.com>
Signed-off-by: NAlek Du <alek.du@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Recent kernel has common method to convert hex digit to its value.
Signed-off-by: NAndy Shevchenko <ext-andriy.shevchenko@nokia.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

The test above allows std to be NULL, so check that std is not NULL before
doing the dereference.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@r exists@
expression E,E1;
identifier f;
statement S1,S2,S3;
@@

if ((E == NULL && ...) || ...)
{
  ... when != if (...) S1 else S2
      when != E = E1
* E->f
  ... when any
}
else S3
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

otg_io_write() function does not follow the declaration of
struct otg_io_access_ops.
Signed-off-by: NIgor Grinberg <grinberg@compulab.co.il>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Fixed coding styles in the core usb endpoint.
Signed-off-by: NCarlos Sánchez Acosta <csanchez@neurowork.net>
Signed-off-by: NAlejandro Sánchez Acosta <asanchez@neurowork.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Fixed coding styles in the core usb driver.
Signed-off-by: NCarlos Sánchez Acosta <csanchez@neurowork.net>
Signed-off-by: NAlejandro Sánchez Acosta <asanchez@neurowork.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Documentation/usb/linux.inf:66: ERROR: trailing whitespace
Documentation/usb/linux.inf:67: ERROR: trailing whitespace
Documentation/usb/linux.inf:98: ERROR: trailing whitespace
Documentation/usb/linux.inf:99: ERROR: trailing whitespace
Documentation/usb/linux.inf:115: ERROR: trailing whitespace
Documentation/usb/linux.inf:116: ERROR: trailing whitespace
Documentation/usb/linux.inf:120: ERROR: trailing whitespace
Documentation/usb/linux.inf:121: ERROR: trailing whitespace
Documentation/usb/linux.inf:122: ERROR: trailing whitespace
Documentation/usb/linux.inf:123: ERROR: trailing whitespace
Documentation/usb/linux.inf:144: ERROR: trailing whitespace
Documentation/usb/linux.inf:145: ERROR: trailing whitespace
Documentation/usb/linux.inf:146: ERROR: trailing whitespace
Documentation/usb/linux.inf:147: ERROR: trailing whitespace
Documentation/usb/linux.inf:158: ERROR: trailing whitespace
Signed-off-by: NAndrea Gelmini <andrea.gelmini@gelma.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Documentation/usb/hotplug.txt:13: ERROR: trailing whitespace
Documentation/usb/hotplug.txt:87: ERROR: trailing whitespace
Signed-off-by: NAndrea Gelmini <andrea.gelmini@gelma.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Documentation/usb/ehci.txt:12: ERROR: trailing whitespace
Signed-off-by: NAndrea Gelmini <andrea.gelmini@gelma.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Use memdup_user when user data is immediately copied into the
allocated region.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression from,to,size,flag;
position p;
identifier l1,l2;
@@

-  to = \(kmalloc@p\|kzalloc@p\)(size,flag);
+  to = memdup_user(from,size);
   if (
-      to==NULL
+      IS_ERR(to)
                 || ...) {
   <+... when != goto l1;
-  -ENOMEM
+  PTR_ERR(to)
   ...+>
   }
-  if (copy_from_user(to, from, size) != 0) {
-    <+... when != goto l2;
-    -EFAULT
-    ...+>
-  }
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

This patch (as1382) changes the USB_EHCI_TT_NEWSCHED Kconfig option to
be non-experimental and to default to Y.  This option has existed for
a long time, and I have not heard any complaints concerning it.  By
contrast, several people have reported that their devices could be
made to work only by enabling the option.

The point of changing the default is to cause the option to be enabled
by distros that simply use the default settings for esoteric things
like this.

This change was motivated by Bugzilla #15649.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
CC: David Brownell <david-b@pacbell.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Signed-off-by: NJames Courtier-Dutton <James@superbug.co.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

When code to manipulate the command register was refactored from
xhci_run() to xhci_start(), a debugging statement was left behind that no
longer applies.  Remove that statement.
Signed-off-by: NSarah Sharp <sarah.a.sharp@linux.intel.com>
Reported-by: NSergei Shtylyov <sshtylyov@mvista.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Fixed spacing coding style issues.
Signed-off-by: NNicolas Kaiser <nikai@nikai.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Fixed brace coding style issues.
Signed-off-by: NNicolas Kaiser <nikai@nikai.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

This patch (as1392) fixes a bug in uhci-hcd: The start_rh() routine is
supposed to be called with the private spinlock held.  If an IRQ comes
in at just the wrong time, the driver will think the controller has
died when in fact it simply hasn't start yet.

The patch also addresses some issues that may prevent an URB from
being unlinked after the controller has stopped.  This is an abnormal
occurrence (ordinarily the controller stops only when the entire bus
is suspended and hence there are no active URBs), so the pathways
haven't gotten much testing.  These two changes may be a little more
than is strictly necessary, but clearly they won't hurt.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

This patch (as1391) fixes a problem that can occur when USB host
controller hardware is hot-unplugged.  If no interrupts are generated
by the unplug then the HCD may not realize that the controller is
gone, and the subsequent unbind may hang waiting for interrupts that
never arrive.

The solution (for PCI-based controllers) is to call the HCD's
interrupt handler at the start of usb_hcd_pci_remove().  If the
hardware is gone, the handler will realize this when it tries to read
the controller's status register.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

This patch (as1390) fixes a problem that crops up when a UHCI host
controller is unbound from uhci-hcd while there are still some active
URBs.  The URBs have to be unlinked when the root hub is unregistered,
and uhci-hcd relies upon root-hub status polls as part of its
unlinking procedure.  But usb_hcd_poll_rh_status() won't make those
status calls if hcd->rh_registered is clear, and the flag is cleared
_before_ the unregistration takes place.

Since hcd->rh_registered is used for other things and needs to be
cleared early, the solution is to add a new flag (rh_pollable) and use
it instead.  It gets cleared _after_ the root hub is unregistered.

Now that the status polls don't end too soon, we have to make sure
they also don't occur too late -- after the root hub's usb_device
structure or the HCD's private structures are deallocated.  Therefore
the patch adds usb_get_device() and usb_put_device() calls to protect
the root hub structure, and it adds an extra del_timer_sync() to
prevent the root-hub timer from causing an unexpected status poll.

This additional complexity would not be needed if the HCD framework
had provided separate stop() and release() callbacks instead of just
stop().  This lack could be fixed at some future time (although it
would require changes to every host controller driver); when that
happens this patch won't be needed any more.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

This patch (as1389) fixes some errors in the failure pathway of
usb_add_hcd().  The actions it takes ought to be exactly the same as
those taken by usb_remove_hcd(), but they aren't.

In one case (removal of the usb_bus_attr_group), the two routines are
brought into agreement by changing usb_remove_hcd().  All the other
discrepancies are fixed by changing usb_add_hcd().
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

* 'writable_limits' of git://decibel.fi.muni.cz/~xslaby/linux:
  unistd: add __NR_prlimit64 syscall numbers
  rlimits: implement prlimit64 syscall
  rlimits: switch more rlimit syscalls to do_prlimit
  rlimits: redo do_setrlimit to more generic do_prlimit
  rlimits: add rlimit64 structure
  rlimits: do security check under task_lock
  rlimits: allow setrlimit to non-current tasks
  rlimits: split sys_setrlimit
  rlimits: selinux, do rlimits changes under task_lock
  rlimits: make sure ->rlim_max never grows in sys_setrlimit
  rlimits: add task_struct to update_rlimit_cpu
  rlimits: security, add task_struct to setrlimit

Fix up various system call number conflicts.  We not only added fanotify
system calls in the meantime, but asm-generic/unistd.h added a wait4
along with a range of reserved per-architecture system calls.

* git://git.infradead.org/mtd-2.6: (79 commits)
  mtd: Remove obsolete <mtd/compatmac.h> include
  mtd: Update copyright notices
  jffs2: Update copyright notices
  mtd-physmap: add support users can assign the probe type in board files
  mtd: remove redwood map driver
  mxc_nand: Add v3 (i.MX51) Support
  mxc_nand: support 8bit ecc
  mxc_nand: fix correct_data function
  mxc_nand: add V1_V2 namespace to registers
  mxc_nand: factor out a check_int function
  mxc_nand: make some internally used functions overwriteable
  mxc_nand: rework get_dev_status
  mxc_nand: remove 0xe00 offset from registers
  mtd: denali: Add multi connected NAND support
  mtd: denali: Remove set_ecc_config function
  mtd: denali: Remove unuseful code in get_xx_nand_para functions
  mtd: denali: Remove device_info_tag structure
  mtd: m25p80: add support for the Winbond W25Q32 SPI flash chip
  mtd: m25p80: add support for the Intel/Numonyx {16,32,64}0S33B SPI flash chips
  mtd: m25p80: add support for the EON EN25P{32, 64} SPI flash chips
  ...

Fix up trivial conflicts in drivers/mtd/maps/{Kconfig,redwood.c} due to
redwood driver removal.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/bcopeland/omfs:
  omfs: fix uninitialized variable warning
  omfs: sanity check cluster size
  omfs: refuse to mount if bitmap pointer is obviously wrong
  omfs: check bounds on block numbers before passing to sb_bread
  omfs: fix memory leak

* 'for-linus' of git://git.infradead.org/users/eparis/notify: (132 commits)
  fanotify: use both marks when possible
  fsnotify: pass both the vfsmount mark and inode mark
  fsnotify: walk the inode and vfsmount lists simultaneously
  fsnotify: rework ignored mark flushing
  fsnotify: remove global fsnotify groups lists
  fsnotify: remove group->mask
  fsnotify: remove the global masks
  fsnotify: cleanup should_send_event
  fanotify: use the mark in handler functions
  audit: use the mark in handler functions
  dnotify: use the mark in handler functions
  inotify: use the mark in handler functions
  fsnotify: send fsnotify_mark to groups in event handling functions
  fsnotify: Exchange list heads instead of moving elements
  fsnotify: srcu to protect read side of inode and vfsmount locks
  fsnotify: use an explicit flag to indicate fsnotify_destroy_mark has been called
  fsnotify: use _rcu functions for mark list traversal
  fsnotify: place marks on object in order of group memory address
  vfs/fsnotify: fsnotify_close can delay the final work in fput
  fsnotify: store struct file not struct path
  ...

Fix up trivial delete/modify conflict in fs/notify/inotify/inotify.c.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6: (96 commits)
  no need for list_for_each_entry_safe()/resetting with superblock list
  Fix sget() race with failing mount
  vfs: don't hold s_umount over close_bdev_exclusive() call
  sysv: do not mark superblock dirty on remount
  sysv: do not mark superblock dirty on mount
  btrfs: remove junk sb_dirt change
  BFS: clean up the superblock usage
  AFFS: wait for sb synchronization when needed
  AFFS: clean up dirty flag usage
  cifs: truncate fallout
  mbcache: fix shrinker function return value
  mbcache: Remove unused features
  add f_flags to struct statfs(64)
  pass a struct path to vfs_statfs
  update VFS documentation for method changes.
  All filesystems that need invalidate_inode_buffers() are doing that explicitly
  convert remaining ->clear_inode() to ->evict_inode()
  Make ->drop_inode() just return whether inode needs to be dropped
  fs/inode.c:clear_inode() is gone
  fs/inode.c:evict() doesn't care about delete vs. non-delete paths now
  ...

Fix up trivial conflicts in fs/nilfs2/super.c

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6: (59 commits)
  igbvf.txt: Add igbvf Documentation
  igb.txt: Add igb documentation
  e100/e1000*/igb*/ixgb*: Add missing read memory barrier
  ixgbe: fix build error with FCOE_CONFIG without DCB_CONFIG
  netxen: protect tx timeout recovery by rtnl lock
  isdn: gigaset: use after free
  isdn: gigaset: add missing unlock
  solos-pci: Fix race condition in tasklet RX handling
  pkt_sched: Fix sch_sfq vs tcf_bind_filter oops
  net: disable preemption before call smp_processor_id()
  tcp: no md5sig option size check bug
  iwlwifi: fix locking assertions
  iwlwifi: fix TX tracer
  isdn: fix information leak
  net: Fix napi_gro_frags vs netpoll path
  usbnet: remove noisy and hardly useful printk
  rtl8180: avoid potential NULL deref in rtl8180_beacon_work
  ath9k: Remove myself from the MAINTAINERS list
  libertas: scan before assocation if no BSSID was given
  libertas: fix association with some APs by using extended rates
  ...

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/ide-2.6:
  tx493xide: use min_t() macro instead of min()
  drivers/ide: Use memdup_user
  via82cxxx: fix typo for VT6415 PCIE PATA IDE Host Controller support.
  ide-cd: Do not access completed requests in the irq handler

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc-2.6:
  sparc64: Update defconfig.
  sparc: Kill user copy check code.
  sparc64: Fix perf_arch_get_caller_regs().
  sparc64: Add missing ID to parport probing code.

* 'rs485fix' of git://www.jni.nu/cris:
  CRIS: ioctl for getting RS485 information

* 'merge' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc:
  powerpc: fix build with make 3.82
  Revert "Input: appletouch - fix integer overflow issue"
  memblock: Fix memblock_is_region_reserved() to return a boolean
  powerpc: Trim defconfigs
  powerpc: fix i8042 module build error
  sound/soc: mpc5200_psc_ac97: Use gpio pins for cold reset
  powerpc/5200: add mpc5200_psc_ac97_gpio_reset

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/vapier/blackfin: (32 commits)
  Blackfin: gpio: add a debounce stub
  Blackfin: update defconfigs
  Blackfin: remove CONFIG_MEM_GENERIC_BOARD
  Blackfin: dpmc: punt unnecessary RTC_ISTAT clearing
  Blackfin: unify rotary encoder bitmasks
  Blackfin: unify SDH/RSI bitmasks
  Blackfin: BF54x: tweak DMAC MMR naming to match other ports
  Blackfin: TWI: clean up the MMR names
  Blackfin: add EVT_OVERRIDE/IPRIO core MMR helpers
  Blackfin: add support for dynamic ftrace
  Blackfin: add support for LZO compressed kernels
  Blackfin: portmux: fix peripheral map overflow when requesting pins
  Blackfin: document SPI CS limitations with CPHA=0
  Blackfin: remove useless and outdated documentation
  Blackfin: BF51x/BF52x: support GPIO Hysteresis/Schmitt Trigger options
  Blackfin: gpio/portmux: clean up whitespace corruption
  Blackfin: make sure mmiowb inserts a write barrier with SSYNC
  Blackfin: fix DMA/cache bug when resuming from suspend to RAM
  Blackfin: BF51x: fix handling of PH8 (the "internal" SPI0SEL4 pin)
  Blackfin: add a GPIO_DEFAULT_BOOT_SPI_CS
  ...

* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/djbw/async_tx: (30 commits)
  DMAENGINE: at_hdmac: locking fixlet
  DMAENGINE: pch_dma: kill another usage of __raw_{read|write}l
  dma: dmatest: fix potential sign bug
  ioat2: catch and recover from broken vtd configurations v6
  DMAENGINE: add runtime slave control to COH 901 318 v3
  DMAENGINE: add runtime slave config to DMA40 v3
  DMAENGINE: generic slave channel control v3
  dmaengine: Driver for Topcliff PCH DMA controller
  intel_mid: Add Mrst & Mfld DMA Drivers
  drivers/dma: Eliminate a NULL pointer dereference
  dma/timb_dma: compile warning on 32 bit
  DMAENGINE: ste_dma40: support older silicon
  DMAENGINE: ste_dma40: support disabling physical channels
  DMAENGINE: ste_dma40: no disabled phy channels on ux500
  DMAENGINE: ste_dma40: fix suspend bug
  DMAENGINE: ste_dma40: add DB8500 memcpy channels
  DMAENGINE: ste_dma40: no flow control on memcpy
  DMAENGINE: ste_dma40: arch updates for LCLA and LCPA
  DMAENGINE: ste_dma40: allocate LCLA dynamically
  DMAENGINE: ste_dma40: no premature stop
  ...

Fix up trivial conflicts in arch/arm/mach-ux500/devices-db8500.c

According include/linux/console_struct.h,vc_scr_end is unsigned long.

struct vc_data {
    unsigned short  vc_num;         /* Console number */
    unsigned int    vc_cols;        /* [#] Console size */
    unsigned int    vc_rows;
    unsigned int    vc_size_row;        /* Bytes per row */
    unsigned int    vc_scan_lines;      /* # of scan lines */
    unsigned long   vc_origin;      /* [!] Start of real screen */
    unsigned long   vc_scr_end;     /* [!] End of real screen */
    unsigned long   vc_visible_origin;  /* [!] Top of visible window */
    unsigned int    vc_top, vc_bottom;  /* Scrolling region */
    const struct consw *vc_sw;
    unsigned short  *vc_screenbuf;
...
}
Signed-off-by: Nqiaochong <qiaochong@loongson.cn>
Cc: Greg KH <greg@kroah.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kernel will die on some platform when switch from vga mode to framebuffer
mode.  The reason of this bug is that bind_con_driver reset vc->vc_origin
to (unsigned long)vc->vc_screenbuf.

On vgacon vc->vc_origin is not releated to vc->vc_screenbuf,if set
vc->vc_origin to vc->vc_screenbuf,kernel will die on vc_do_resize.

static int vc_do_resize(struct tty_struct *tty, struct tty_struct *real_tty,
        struct vc_data *vc, unsigned int cols, unsigned int lines)
{
    unsigned long old_origin, new_origin, new_scr_end, rlth, rrem, err = 0;
    unsigned int old_cols, old_rows, old_row_size, old_screen_size;
    unsigned int new_cols, new_rows, new_row_size, new_screen_size;
    unsigned int end, user;
...
        end = (old_rows > new_rows) ? old_origin +
            (old_row_size * new_rows) :
            vc->vc_scr_end;

...
/*
here for a test from vgacon to framebuffer:
old_origin=0x810814a0,end=0xb00b8fa0,vc->vc_origin=0x810814a0
the code bellow will copy memory from 0x810814a0 to 0xb00b8fa0,
this will cover kernel code,kernel died here.
*/

    while (old_origin < end) {

        scr_memcpyw((unsigned short *) new_origin,
                (unsigned short *) old_origin, rlth);
        if (rrem)
            scr_memsetw((void *)(new_origin + rlth),
                    vc->vc_video_erase_char, rrem);
        old_origin += old_row_size;
        new_origin += new_row_size;
    }

...
}

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Nqiaochong <qiaochong@loongson.cn>
Cc: Greg KH <greg@kroah.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

More code can be pushed from rwsem_down_read_failed and
rwsem_down_write_failed into rwsem_down_failed_common.

Following change adding down_read_critical infrastructure support also
enjoys having flags available in a register rather than having to fish it
out in the struct rwsem_waiter...
Signed-off-by: NMichel Lespinasse <walken@google.com>
Acked-by: NDavid Howells <dhowells@redhat.com>
Cc: Mike Waychison <mikew@google.com>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Ying Han <yinghan@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This change addresses the following situation:

- Thread A acquires the rwsem for read
- Thread B tries to acquire the rwsem for write, notices there is already
  an active owner for the rwsem.
- Thread C tries to acquire the rwsem for read, notices that thread B already
  tried to acquire it.
- Thread C grabs the spinlock and queues itself on the wait queue.
- Thread B grabs the spinlock and queues itself behind C. At this point A is
  the only remaining active owner on the rwsem.

In this situation thread B could notice that it was the last active writer
on the rwsem, and decide to wake C to let it proceed in parallel with A
since they both only want the rwsem for read.
Signed-off-by: NMichel Lespinasse <walken@google.com>
Acked-by: NDavid Howells <dhowells@redhat.com>
Cc: Mike Waychison <mikew@google.com>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Ying Han <yinghan@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Previously each waiting thread added a bias of RWSEM_WAITING_BIAS.  With
this change, the bias is added only once to indicate that the wait list is
non-empty.

This has a few nice properties which will be used in following changes:
- when the spinlock is held and the waiter list is known to be non-empty,
  count < RWSEM_WAITING_BIAS  <=>  there is an active writer on that sem
- count == RWSEM_WAITING_BIAS  <=>  there are waiting threads and no
                                     active readers/writers on that sem
Signed-off-by: NMichel Lespinasse <walken@google.com>
Acked-by: NDavid Howells <dhowells@redhat.com>
Cc: Mike Waychison <mikew@google.com>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Ying Han <yinghan@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In __rwsem_do_wake(), we can skip the active count check unless we come
there from up_xxxx().  Also when checking the active count, it is not
actually necessary to increment it; this allows us to get rid of the read
side undo code and simplify the calculation of the final rwsem count
adjustment once we've counted the reader threads to wake.

The basic observation is the following.  When there are waiter threads on
a rwsem and the spinlock is held, other threads can only increment the
active count by trying to grab the rwsem in down_xxxx().  However
down_xxxx() will notice there are waiter threads and take the down_failed
path, blocking to acquire the spinlock on the way there.  Therefore, a
thread observing an active count of zero with waiters queued and the
spinlock held, is protected against other threads acquiring the rwsem
until it wakes the last waiter or releases the spinlock.
Signed-off-by: NMichel Lespinasse <walken@google.com>
Acked-by: NDavid Howells <dhowells@redhat.com>
Cc: Mike Waychison <mikew@google.com>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Ying Han <yinghan@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>