A big problem with rcu protected data structures that are also reference
counted is that you must jump through several hoops to increase the reference
count. I think someone finally implemented atomic_inc_not_zero(&count) to
automate the common case. Unfortunately this means you must special case the
rcu access case.
When data structures are only visible via rcu in a manner that is not
determined by the reference count on the object (i.e. tasks are visible until
their zombies are reaped) there is a much simpler technique we can employ.
Simply delaying the decrement of the reference count until the rcu interval is
over.
What that means is that the proc code that looks up a task and later
wants to sleep can now do:
rcu_read_lock();
task = find_task_by_pid(some_pid);
if (task) {
get_task_struct(task);
}
rcu_read_unlock();
The effect on the rest of the kernel is that put_task_struct becomes cheaper
and immediate, and in the case where the task has been reaped it frees the
task immediate instead of unnecessarily waiting an until the rcu interval is
over.
Cleanup of task_struct does not happen when its reference count drops to
zero, instead cleanup happens when release_task is called. Tasks can only
be looked up via rcu before release_task is called. All rcu protected
members of task_struct are freed by release_task.
Therefore we can move call_rcu from put_task_struct into release_task. And
we can modify release_task to not immediately release the reference count
but instead have it call put_task_struct from the function it gives to
call_rcu.
The end result:
- get_task_struct is safe in an rcu context where we have just looked
up the task.
- put_task_struct() simplifies into its old pre rcu self.
This reorganization also makes put_task_struct uncallable from modules as
it is not exported but it does not appear to be called from any modules so
this should not be an issue, and is trivially fixed.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This just got nuked in mainline. Bring it back because Eric's patches use it.
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
To increase the strength of SCHED_BATCH as a scheduling hint we can
activate batch tasks on the expired array since by definition they are
latency insensitive tasks.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The activated flag in task_struct is used to track different sleep types and
its usage is somewhat obfuscated. Convert the variable to an enum with more
descriptive names without altering the function.
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Currently, count_active_tasks() calls both nr_running() &
nr_interruptible(). Each of these functions does a "for_each_cpu" & reads
values from the runqueue of each cpu. Although this is not a lot of
instructions, each runqueue may be located on different node. Depending on
the architecture, a unique TLB entry may be required to access each
runqueue.
Since there may be more runqueues than cpu TLB entries, a scan of all
runqueues can trash the TLB. Each memory reference incurs a TLB miss &
refill.
In addition, the runqueue cacheline that contains nr_running &
nr_uninterruptible may be evicted from the cache between the two passes.
This causes unnecessary cache misses.
Combining nr_running() & nr_interruptible() into a single function
substantially reduces the TLB & cache misses on large systems. This should
have no measureable effect on smaller systems.
On a 128p IA64 system running a memory stress workload, the new function
reduced the overhead of calc_load() from 605 usec/call to 324 usec/call.
Signed-off-by: Jack Steiner <steiner@sgi.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The removal of the data field in the hrtimer structure enforces the
embedding of the timer into another data structure. nanosleep now uses a
private implementation of the most common used timer callback function
(simple task wakeup).
In order to avoid the reimplentation of such functionality all over the
place a generic hrtimer_sleeper functionality is created.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add support for LED triggers to the LED subsystem. "Triggers" are events
which change the state of an LED. Two kinds of trigger are available, simple
ones which can be added to exising code with minimum disruption and complex
ones for implementing new or more complex functionality.
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add the foundations of a new LEDs subsystem. This patch adds a class which
presents LED devices within sysfs and allows their brightness to be
controlled.
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add TIOCL_GETKMSGREDIRECT needed by the userland suspend tool to get the
current value of kmsg_redirect from the kernel so that it can save it and
restore it after resume.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@suse.cz>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove the recently-added LINUX_FADV_ASYNC_WRITE and LINUX_FADV_WRITE_WAIT
fadvise() additions, do it in a new sys_sync_file_range() syscall instead.
Reasons:
- It's more flexible. Things which would require two or three syscalls with
fadvise() can be done in a single syscall.
- Using fadvise() in this manner is something not covered by POSIX.
The patch wires up the syscall for x86.
The sycall is implemented in the new fs/sync.c. The intention is that we can
move sys_fsync(), sys_fdatasync() and perhaps sys_sync() into there later.
Documentation for the syscall is in fs/sync.c.
A test app (sync_file_range.c) is in
http://www.zip.com.au/~akpm/linux/patches/stuff/ext3-tools.tar.gz.
The available-to-GPL-modules do_sync_file_range() is for knfsd: "A COMMIT can
say NFS_DATA_SYNC or NFS_FILE_SYNC. I can skip the ->fsync call for
NFS_DATA_SYNC which is hopefully the more common."
Note: the `async' writeout mode SYNC_FILE_RANGE_WRITE will turn synchronous if
the queue is congested. This is trivial to fix: add a new flag bit, set
wbc->nonblocking. But I'm not sure that we want to expose implementation
details down to that level.
Note: it's notable that we can sync an fd which wasn't opened for writing.
Same with fsync() and fdatasync()).
Note: the code takes some care to handle attempts to sync file contents
outside the 16TB offset on 32-bit machines. It makes such attempts appear to
succeed, for best 32-bit/64-bit compatibility. Perhaps it should make such
requests fail...
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Cc: Ulrich Drepper <drepper@redhat.com>
Cc: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Matt Domsch noticed a startup race with the IPMI kernel thread, it was
possible (though extraordinarly unlikely) that a message could come in
before the upper layer was ready to handle it. This patch splits the
startup processing of an IPMI interface into two parts, one to get ready
and one to actually start the processes to receive messages from the
interface.
[akpm@osdl.org: cleanups]
Signed-off-by: Corey Minyard <minyard@acm.org>
Cc: Matt Domsch <Matt_Domsch@dell.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Make baby-simple the code for /proc/devices. Based on the proven design
for /proc/interrupts.
This also fixes the early-termination regression 2.6.16 introduced, as
demonstrated by:
# dd if=/proc/devices bs=1
Character devices:
1 mem
27+0 records in
27+0 records out
This should also work (but is untested) when /proc/devices >4096 bytes,
which I believe is what the original 2.6.16 rewrite fixed.
[akpm@osdl.org: cleanups, simplifications]
Signed-off-by: Joe Korty <joe.korty@ccur.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Commit a4a6198b80:
[PATCH] tvec_bases too large for per-cpu data
introduced "struct tvec_t_base_s boot_tvec_bases" which is visible at
compile time. This means we can kill __init_timer_base and move
timer_base_s's content into tvec_t_base_s.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
find_trylock_page() is an odd interface in that it doesn't take a reference
like the others. Now that XFS no longer uses it, and its last remaining
caller actually wants an elevated refcount, opencode that callsite and
schedule find_trylock_page() for removal.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
- chips/sharp.c: make two needlessly global functions static
- move some declarations to a header file where they belong to
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Semaphore to mutex conversion.
The conversion was generated via scripts, and the result was validated
automatically via a script as well.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Previously we added NET_IP_ALIGN so an architecture can override the
padding done to align headers. The next step is to allow the skb
headroom to be overridden.
We currently always reserve 16 bytes to grow into, meaning all DMAs
start 16 bytes into a cacheline. On ppc64 we really want DMA writes to
start on a cacheline boundary, so we increase that headroom to one
cacheline.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
* 'upstream-linus' of master.kernel.org:/pub/scm/linux/kernel/git/jgarzik/libata-dev:
[PATCH] sata_mv: three bug fixes
[PATCH] libata: ata_dev_init_params() fixes
[PATCH] libata: Fix interesting use of "extern" and also some bracketing
[PATCH] libata: Simplex and other mode filtering logic
[PATCH] libata - ATA is both ATA and CFA
[PATCH] libata: Add ->set_mode hook for odd drivers
[PATCH] libata: BMDMA handling updates
[PATCH] libata: kill trailing whitespace
[PATCH] libata: add FIXME above ata_dev_xfermask()
[PATCH] libata: cosmetic changes in ata_bus_softreset()
[PATCH] libata: kill E.D.D.
This enables the caller to migrate pages from one address space page
cache to another. In buzz word marketing, you can do zero-copy file
copies!
Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This adds support for the sys_splice system call. Using a pipe as a
transport, it can connect to files or sockets (latter as output only).
From the splice.c comments:
"splice": joining two ropes together by interweaving their strands.
This is the "extended pipe" functionality, where a pipe is used as
an arbitrary in-memory buffer. Think of a pipe as a small kernel
buffer that you can use to transfer data from one end to the other.
The traditional unix read/write is extended with a "splice()" operation
that transfers data buffers to or from a pipe buffer.
Named by Larry McVoy, original implementation from Linus, extended by
Jens to support splicing to files and fixing the initial implementation
bugs.
Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add a field to the host_set called 'flags' (was host_set_flags changed
to suit Jeff)
Add a simplex_claimed field so we can remember who owns the DMA channel
Add a ->mode_filter() hook to allow drivers to filter modes
Add docs for mode_filter and set_mode
Filter according to simplex state
Filter cable in core
This provides the needed framework to support all the mode rules found
in the PATA world. The simplex filter deals with 'to spec' simplex DMA
systems found in older chips. The cable filter avoids duplicating the
same rules in each chip driver with PATA. Finally the mode filter is
neccessary because drive/chip combinations have errata that forbid
certain modes with some drives or types of ATA object.
Drive speed setup remains per channel for now and the filters now use
the framework Tejun put into place which cleans them up a lot from the
older libata-pata patches.
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Some hardware doesn't want the usual mode setup logic running. This
allows the hardware driver to replace it for special cases in the least
invasive way possible.
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
This is the minimal patch set to enable the current code to be used with
a controller following SFF (ie any PATA and early SATA controllers)
safely without crashes if there is no BMDMA area or if BMDMA is not
assigned by the BIOS for some reason.
Simplex status is recorded but not acted upon in this change, this isn't
a problem with the current drivers as none of them are for simplex
hardware. A following diff will deal with that.
The flags in the probe structure remain ->host_set_flags although Jeff
asked me to rename them, simply because the rename would break the usual
Linux rules that old code should break when there are changes. not
compile and run and then blow up/eat your computer/etc. Renaming this
later is a trivial exercise once a better name is chosen.
Signed-off-by: Jeff Garzik <jeff@garzik.org>
