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	fs/block_dev.c

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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Jens Axboe committed Apr 29, 2010
2 parents 6a47dc1 + 79dba2e commit 7407cf3
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2 changes: 1 addition & 1 deletion Documentation/HOWTO
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Expand Up @@ -234,7 +234,7 @@ process is as follows:
Linus, usually the patches that have already been included in the
-next kernel for a few weeks. The preferred way to submit big changes
is using git (the kernel's source management tool, more information
can be found at http://git.or.cz/) but plain patches are also just
can be found at http://git-scm.com/) but plain patches are also just
fine.
- After two weeks a -rc1 kernel is released it is now possible to push
only patches that do not include new features that could affect the
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39 changes: 22 additions & 17 deletions Documentation/RCU/NMI-RCU.txt
Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ NMI handler.
cpu = smp_processor_id();
++nmi_count(cpu);

if (!rcu_dereference(nmi_callback)(regs, cpu))
if (!rcu_dereference_sched(nmi_callback)(regs, cpu))
default_do_nmi(regs);

nmi_exit();
Expand All @@ -47,12 +47,13 @@ function pointer. If this handler returns zero, do_nmi() invokes the
default_do_nmi() function to handle a machine-specific NMI. Finally,
preemption is restored.

Strictly speaking, rcu_dereference() is not needed, since this code runs
only on i386, which does not need rcu_dereference() anyway. However,
it is a good documentation aid, particularly for anyone attempting to
do something similar on Alpha.
In theory, rcu_dereference_sched() is not needed, since this code runs
only on i386, which in theory does not need rcu_dereference_sched()
anyway. However, in practice it is a good documentation aid, particularly
for anyone attempting to do something similar on Alpha or on systems
with aggressive optimizing compilers.

Quick Quiz: Why might the rcu_dereference() be necessary on Alpha,
Quick Quiz: Why might the rcu_dereference_sched() be necessary on Alpha,
given that the code referenced by the pointer is read-only?


Expand Down Expand Up @@ -99,17 +100,21 @@ invoke irq_enter() and irq_exit() on NMI entry and exit, respectively.

Answer to Quick Quiz

Why might the rcu_dereference() be necessary on Alpha, given
Why might the rcu_dereference_sched() be necessary on Alpha, given
that the code referenced by the pointer is read-only?

Answer: The caller to set_nmi_callback() might well have
initialized some data that is to be used by the
new NMI handler. In this case, the rcu_dereference()
would be needed, because otherwise a CPU that received
an NMI just after the new handler was set might see
the pointer to the new NMI handler, but the old
pre-initialized version of the handler's data.

More important, the rcu_dereference() makes it clear
to someone reading the code that the pointer is being
protected by RCU.
initialized some data that is to be used by the new NMI
handler. In this case, the rcu_dereference_sched() would
be needed, because otherwise a CPU that received an NMI
just after the new handler was set might see the pointer
to the new NMI handler, but the old pre-initialized
version of the handler's data.

This same sad story can happen on other CPUs when using
a compiler with aggressive pointer-value speculation
optimizations.

More important, the rcu_dereference_sched() makes it
clear to someone reading the code that the pointer is
being protected by RCU-sched.
7 changes: 4 additions & 3 deletions Documentation/RCU/checklist.txt
Original file line number Diff line number Diff line change
Expand Up @@ -260,7 +260,8 @@ over a rather long period of time, but improvements are always welcome!
The reason that it is permissible to use RCU list-traversal
primitives when the update-side lock is held is that doing so
can be quite helpful in reducing code bloat when common code is
shared between readers and updaters.
shared between readers and updaters. Additional primitives
are provided for this case, as discussed in lockdep.txt.

10. Conversely, if you are in an RCU read-side critical section,
and you don't hold the appropriate update-side lock, you -must-
Expand Down Expand Up @@ -344,8 +345,8 @@ over a rather long period of time, but improvements are always welcome!
requiring SRCU's read-side deadlock immunity or low read-side
realtime latency.

Note that, rcu_assign_pointer() and rcu_dereference() relate to
SRCU just as they do to other forms of RCU.
Note that, rcu_assign_pointer() relates to SRCU just as they do
to other forms of RCU.

15. The whole point of call_rcu(), synchronize_rcu(), and friends
is to wait until all pre-existing readers have finished before
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28 changes: 26 additions & 2 deletions Documentation/RCU/lockdep.txt
Original file line number Diff line number Diff line change
Expand Up @@ -32,9 +32,20 @@ checking of rcu_dereference() primitives:
srcu_dereference(p, sp):
Check for SRCU read-side critical section.
rcu_dereference_check(p, c):
Use explicit check expression "c".
Use explicit check expression "c". This is useful in
code that is invoked by both readers and updaters.
rcu_dereference_raw(p)
Don't check. (Use sparingly, if at all.)
rcu_dereference_protected(p, c):
Use explicit check expression "c", and omit all barriers
and compiler constraints. This is useful when the data
structure cannot change, for example, in code that is
invoked only by updaters.
rcu_access_pointer(p):
Return the value of the pointer and omit all barriers,
but retain the compiler constraints that prevent duplicating
or coalescsing. This is useful when when testing the
value of the pointer itself, for example, against NULL.

The rcu_dereference_check() check expression can be any boolean
expression, but would normally include one of the rcu_read_lock_held()
Expand All @@ -59,7 +70,20 @@ In case (1), the pointer is picked up in an RCU-safe manner for vanilla
RCU read-side critical sections, in case (2) the ->file_lock prevents
any change from taking place, and finally, in case (3) the current task
is the only task accessing the file_struct, again preventing any change
from taking place.
from taking place. If the above statement was invoked only from updater
code, it could instead be written as follows:

file = rcu_dereference_protected(fdt->fd[fd],
lockdep_is_held(&files->file_lock) ||
atomic_read(&files->count) == 1);

This would verify cases #2 and #3 above, and furthermore lockdep would
complain if this was used in an RCU read-side critical section unless one
of these two cases held. Because rcu_dereference_protected() omits all
barriers and compiler constraints, it generates better code than do the
other flavors of rcu_dereference(). On the other hand, it is illegal
to use rcu_dereference_protected() if either the RCU-protected pointer
or the RCU-protected data that it points to can change concurrently.

There are currently only "universal" versions of the rcu_assign_pointer()
and RCU list-/tree-traversal primitives, which do not (yet) check for
Expand Down
6 changes: 6 additions & 0 deletions Documentation/RCU/whatisRCU.txt
Original file line number Diff line number Diff line change
Expand Up @@ -840,6 +840,12 @@ SRCU: Initialization/cleanup
init_srcu_struct
cleanup_srcu_struct

All: lockdep-checked RCU-protected pointer access

rcu_dereference_check
rcu_dereference_protected
rcu_access_pointer

See the comment headers in the source code (or the docbook generated
from them) for more information.

Expand Down
3 changes: 1 addition & 2 deletions Documentation/cgroups/cgroups.txt
Original file line number Diff line number Diff line change
Expand Up @@ -235,8 +235,7 @@ containing the following files describing that cgroup:
- cgroup.procs: list of tgids in the cgroup. This list is not
guaranteed to be sorted or free of duplicate tgids, and userspace
should sort/uniquify the list if this property is required.
Writing a tgid into this file moves all threads with that tgid into
this cgroup.
This is a read-only file, for now.
- notify_on_release flag: run the release agent on exit?
- release_agent: the path to use for release notifications (this file
exists in the top cgroup only)
Expand Down
23 changes: 17 additions & 6 deletions Documentation/input/multi-touch-protocol.txt
Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,22 @@ like:
SYN_MT_REPORT
SYN_REPORT

Here is the sequence after lifting one of the fingers:

ABS_MT_POSITION_X
ABS_MT_POSITION_Y
SYN_MT_REPORT
SYN_REPORT

And here is the sequence after lifting the remaining finger:

SYN_MT_REPORT
SYN_REPORT

If the driver reports one of BTN_TOUCH or ABS_PRESSURE in addition to the
ABS_MT events, the last SYN_MT_REPORT event may be omitted. Otherwise, the
last SYN_REPORT will be dropped by the input core, resulting in no
zero-finger event reaching userland.

Event Semantics
---------------
Expand Down Expand Up @@ -217,11 +233,6 @@ where examples can be found.
difference between the contact position and the approaching tool position
could be used to derive tilt.
[2] The list can of course be extended.
[3] The multi-touch X driver is currently in the prototyping stage. At the
time of writing (April 2009), the MT protocol is not yet merged, and the
prototype implements finger matching, basic mouse support and two-finger
scrolling. The project aims at improving the quality of current multi-touch
functionality available in the Synaptics X driver, and in addition
implement more advanced gestures.
[3] Multitouch X driver project: http://bitmath.org/code/multitouch/.
[4] See the section on event computation.
[5] See the section on finger tracking.
7 changes: 1 addition & 6 deletions Documentation/kernel-parameters.txt
Original file line number Diff line number Diff line change
Expand Up @@ -320,11 +320,6 @@ and is between 256 and 4096 characters. It is defined in the file
amd_iommu= [HW,X86-84]
Pass parameters to the AMD IOMMU driver in the system.
Possible values are:
isolate - enable device isolation (each device, as far
as possible, will get its own protection
domain) [default]
share - put every device behind one IOMMU into the
same protection domain
fullflush - enable flushing of IO/TLB entries when
they are unmapped. Otherwise they are
flushed before they will be reused, which
Expand Down Expand Up @@ -1199,7 +1194,7 @@ and is between 256 and 4096 characters. It is defined in the file

libata.force= [LIBATA] Force configurations. The format is comma
separated list of "[ID:]VAL" where ID is
PORT[:DEVICE]. PORT and DEVICE are decimal numbers
PORT[.DEVICE]. PORT and DEVICE are decimal numbers
matching port, link or device. Basically, it matches
the ATA ID string printed on console by libata. If
the whole ID part is omitted, the last PORT and DEVICE
Expand Down
76 changes: 46 additions & 30 deletions Documentation/networking/timestamping.txt
Original file line number Diff line number Diff line change
Expand Up @@ -41,11 +41,12 @@ SOF_TIMESTAMPING_SOFTWARE: return system time stamp generated in
SOF_TIMESTAMPING_TX/RX determine how time stamps are generated.
SOF_TIMESTAMPING_RAW/SYS determine how they are reported in the
following control message:
struct scm_timestamping {
struct timespec systime;
struct timespec hwtimetrans;
struct timespec hwtimeraw;
};

struct scm_timestamping {
struct timespec systime;
struct timespec hwtimetrans;
struct timespec hwtimeraw;
};

recvmsg() can be used to get this control message for regular incoming
packets. For send time stamps the outgoing packet is looped back to
Expand Down Expand Up @@ -87,12 +88,13 @@ by the network device and will be empty without that support.
SIOCSHWTSTAMP:

Hardware time stamping must also be initialized for each device driver
that is expected to do hardware time stamping. The parameter is:
that is expected to do hardware time stamping. The parameter is defined in
/include/linux/net_tstamp.h as:

struct hwtstamp_config {
int flags; /* no flags defined right now, must be zero */
int tx_type; /* HWTSTAMP_TX_* */
int rx_filter; /* HWTSTAMP_FILTER_* */
int flags; /* no flags defined right now, must be zero */
int tx_type; /* HWTSTAMP_TX_* */
int rx_filter; /* HWTSTAMP_FILTER_* */
};

Desired behavior is passed into the kernel and to a specific device by
Expand Down Expand Up @@ -139,42 +141,56 @@ enum {
/* time stamp any incoming packet */
HWTSTAMP_FILTER_ALL,

/* return value: time stamp all packets requested plus some others */
HWTSTAMP_FILTER_SOME,
/* return value: time stamp all packets requested plus some others */
HWTSTAMP_FILTER_SOME,

/* PTP v1, UDP, any kind of event packet */
HWTSTAMP_FILTER_PTP_V1_L4_EVENT,

...
/* for the complete list of values, please check
* the include file /include/linux/net_tstamp.h
*/
};


DEVICE IMPLEMENTATION

A driver which supports hardware time stamping must support the
SIOCSHWTSTAMP ioctl. Time stamps for received packets must be stored
in the skb with skb_hwtstamp_set().
SIOCSHWTSTAMP ioctl and update the supplied struct hwtstamp_config with
the actual values as described in the section on SIOCSHWTSTAMP.

Time stamps for received packets must be stored in the skb. To get a pointer
to the shared time stamp structure of the skb call skb_hwtstamps(). Then
set the time stamps in the structure:

struct skb_shared_hwtstamps {
/* hardware time stamp transformed into duration
* since arbitrary point in time
*/
ktime_t hwtstamp;
ktime_t syststamp; /* hwtstamp transformed to system time base */
};

Time stamps for outgoing packets are to be generated as follows:
- In hard_start_xmit(), check if skb_hwtstamp_check_tx_hardware()
returns non-zero. If yes, then the driver is expected
to do hardware time stamping.
- In hard_start_xmit(), check if skb_tx(skb)->hardware is set no-zero.
If yes, then the driver is expected to do hardware time stamping.
- If this is possible for the skb and requested, then declare
that the driver is doing the time stamping by calling
skb_hwtstamp_tx_in_progress(). A driver not supporting
hardware time stamping doesn't do that. A driver must never
touch sk_buff::tstamp! It is used to store how time stamping
for an outgoing packets is to be done.
that the driver is doing the time stamping by setting the field
skb_tx(skb)->in_progress non-zero. You might want to keep a pointer
to the associated skb for the next step and not free the skb. A driver
not supporting hardware time stamping doesn't do that. A driver must
never touch sk_buff::tstamp! It is used to store software generated
time stamps by the network subsystem.
- As soon as the driver has sent the packet and/or obtained a
hardware time stamp for it, it passes the time stamp back by
calling skb_hwtstamp_tx() with the original skb, the raw
hardware time stamp and a handle to the device (necessary
to convert the hardware time stamp to system time). If obtaining
the hardware time stamp somehow fails, then the driver should
not fall back to software time stamping. The rationale is that
this would occur at a later time in the processing pipeline
than other software time stamping and therefore could lead
to unexpected deltas between time stamps.
- If the driver did not call skb_hwtstamp_tx_in_progress(), then
hardware time stamp. skb_hwtstamp_tx() clones the original skb and
adds the timestamps, therefore the original skb has to be freed now.
If obtaining the hardware time stamp somehow fails, then the driver
should not fall back to software time stamping. The rationale is that
this would occur at a later time in the processing pipeline than other
software time stamping and therefore could lead to unexpected deltas
between time stamps.
- If the driver did not call set skb_tx(skb)->in_progress, then
dev_hard_start_xmit() checks whether software time stamping
is wanted as fallback and potentially generates the time stamp.
9 changes: 4 additions & 5 deletions Documentation/stable_kernel_rules.txt
Original file line number Diff line number Diff line change
Expand Up @@ -18,16 +18,15 @@ Rules on what kind of patches are accepted, and which ones are not, into the
- It cannot contain any "trivial" fixes in it (spelling changes,
whitespace cleanups, etc).
- It must follow the Documentation/SubmittingPatches rules.
- It or an equivalent fix must already exist in Linus' tree. Quote the
respective commit ID in Linus' tree in your patch submission to -stable.
- It or an equivalent fix must already exist in Linus' tree (upstream).


Procedure for submitting patches to the -stable tree:

- Send the patch, after verifying that it follows the above rules, to
stable@kernel.org.
- To have the patch automatically included in the stable tree, add the
the tag
stable@kernel.org. You must note the upstream commit ID in the changelog
of your submission.
- To have the patch automatically included in the stable tree, add the tag
Cc: stable@kernel.org
in the sign-off area. Once the patch is merged it will be applied to
the stable tree without anything else needing to be done by the author
Expand Down
9 changes: 4 additions & 5 deletions MAINTAINERS
Original file line number Diff line number Diff line change
Expand Up @@ -485,8 +485,8 @@ S: Maintained
F: drivers/input/mouse/bcm5974.c

APPLE SMC DRIVER
M: Nicolas Boichat <nicolas@boichat.ch>
L: mactel-linux-devel@lists.sourceforge.net
M: Henrik Rydberg <rydberg@euromail.se>
L: lm-sensors@lm-sensors.org
S: Maintained
F: drivers/hwmon/applesmc.c

Expand Down Expand Up @@ -1960,7 +1960,7 @@ F: lib/kobj*

DRM DRIVERS
M: David Airlie <airlied@linux.ie>
L: dri-devel@lists.sourceforge.net
L: dri-devel@lists.freedesktop.org
T: git git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6.git
S: Maintained
F: drivers/gpu/drm/
Expand Down Expand Up @@ -4791,12 +4791,11 @@ F: drivers/s390/crypto/

S390 ZFCP DRIVER
M: Christof Schmitt <christof.schmitt@de.ibm.com>
M: Martin Peschke <mp3@de.ibm.com>
M: Swen Schillig <swen@vnet.ibm.com>
M: linux390@de.ibm.com
L: linux-s390@vger.kernel.org
W: http://www.ibm.com/developerworks/linux/linux390/
S: Supported
F: Documentation/s390/zfcpdump.txt
F: drivers/s390/scsi/zfcp_*

S390 IUCV NETWORK LAYER
Expand Down
4 changes: 2 additions & 2 deletions Makefile
Original file line number Diff line number Diff line change
@@ -1,8 +1,8 @@
VERSION = 2
PATCHLEVEL = 6
SUBLEVEL = 34
EXTRAVERSION = -rc4
NAME = Man-Eating Seals of Antiquity
EXTRAVERSION = -rc5
NAME = Sheep on Meth

# *DOCUMENTATION*
# To see a list of typical targets execute "make help"
Expand Down
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