kthread: Document ways of reducing OS jitter due to per-CPU kthreads

The Linux kernel uses a number of per-CPU kthreads, any of which might
contribute to OS jitter at any time.  The usual approach to normal
kthreads, namely to bind them to a "housekeeping" CPU, does not work
with these kthreads because they cannot operate correctly if moved to
some other CPU.  This commit therefore lists ways of controlling OS
jitter from the Linux kernel's per-CPU kthreads.  It also lists some
ways of diagnosing excessive jitter.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Olivier Baetz <olivier.baetz@novasparks.com>
Cc: Pradeep Satyanarayana <pradeeps@linux.vnet.ibm.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Merge branch 'rcu/doc' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/urgent

Pull RCU documentation update for reducing OS jitter due to
per-CPU kthreads, from Paul McKenney.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
target: Remove unused struct members in se_dev_entry

Some were incremented, but never used anywhere from what I could tell.

Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
target: Use FD_MAX_SECTORS/FD_BLOCKSIZE for blockdevs using fileio

We can still see the error reported in

https://patchwork.kernel.org/patch/2338981/

when using fileio backed by a block device.

I'm assuming this will get us past that error (from sbc_parse_cdb),
and also assuming it's OK to have our max_sectors be larger than
the block's queue max hw sectors?

Reported-by: Eric Harney <eharney@redhat.com>
Signed-off-by: Andy Grover <agrover@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
target: Have dev/enable show if TCM device is configured

User tools need to know if the device is properly configured, since if
not, some other attributes are invalid.

Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
iscsi-target: Fix NULL pointer dereference in iscsit_send_reject

Fix up a NULL pointer dereference regression in iscsit_send_reject()
introduced by from commit 2ec5a8c11.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
iscsi-target: Make buf param of iscsit_do_crypto_hash_buf() const void *

Make the "buf" input param of iscsit_do_crypto_hash_buf() "const void *".
This allows to remove lots of casts in its callers.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
ARM: finally enable IRQ time accounting config

We've had IRQ time accounting for the last six months, except for the
Kconfig symbol.  This somehow got missed out of the original patch.
Add this now.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Merge branch 'linus' into core/urgent

Update with Linus tree so fixes for the same can be applied.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
idle: Fix hlt/nohlt command-line handling in new generic idle

commit d1669912 (idle: Implement generic idle function) added a new
generic idle along with support for hlt/nohlt command line options to
override default idle loop behavior.  However, the command-line
processing is never compiled.

The command-line handling is wrapped by CONFIG_GENERIC_IDLE_POLL_SETUP
and arches that use this feature select it in their Kconfigs.
However, no Kconfig definition was created for this option, so it is
never enabled, and therefore command-line override of the idle-loop
behavior is broken after migrating to the generic idle loop.

To fix, add a Kconfig definition for GENERIC_IDLE_POLL_SETUP.

Tested on ARM (OMAP4/Panda) which enables the command-line overrides
by default.

Signed-off-by: Kevin Hilman <khilman@linaro.org>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linaro-kernel@lists.linaro.org
Link: http://lkml.kernel.org/r/1366849153-25564-1-git-send-email-khilman@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
tick: Use zalloc_cpumask_var for allocating offstack cpumasks

commit b352bc1cbc (tick: Convert broadcast cpu bitmaps to
cpumask_var_t) broke CONFIG_CPUMASK_OFFSTACK in a very subtle way.

Instead of allocating the cpumasks with zalloc_cpumask_var it uses
alloc_cpumask_var, so we can get random data there, which of course
confuses the logic completely and causes random failures.

Reported-and-tested-by: Dave Jones <davej@redhat.com>
Reported-and-tested-by: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1305032015060.2990@ionos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
ARM: 7711/1: dove: fix Dove cpu type from V7 to PJ4

The CPU used in Marvell Dove SoCs is a PJ4 Sheeva core. Using
CONFIG_CPU_PJ4 instead of CONFIG_CPU_V7 will enable iWMMXt
extensions on Dove.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
ARM: 7712/1: Remove trailing whitespace in arch/arm/Makefile

Clean up some trailing whitespace issues in arch/arm/Makefile.

Signed-off-by: Daniel Tang <dt.tangr@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
perf: Fix EXIT event notification

The perf_event_task_ctx() function needs to be called with
preemption disabled, since it's checking for currently
scheduled cpu against event cpu.

We disable preemption for task related perf event context
if there's one defined, leaving up to the chance which cpu
it gets scheduled in.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/1367857638-27631-2-git-send-email-jolsa@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
perf: Factor out auxiliary events notification

Add perf_event_aux() function to send out all types of
auxiliary events - mmap, task, comm events. For each type
there's match and output functions defined and used as
callbacks during perf_event_aux processing.

This way we can centralize the pmu/context iterating and
event matching logic. Also since lot of the code was
duplicated, this patch reduces the .text size about 2kB
on my setup:

  snipped output from 'objdump -x kernel/events/core.o'

  before:
  Idx Name          Size
    0 .text         0000d313

  after:
  Idx Name          Size
    0 .text         0000cad3

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/1367857638-27631-3-git-send-email-jolsa@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
x86: Fix idle consolidation fallout

The core code expects the arch idle code to return with interrupts
enabled. The conversion missed two x86 cases which fail to do that.

Reported-and-tested-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Tested-by: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1305021557030.3972@ionos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
iscsi-target: Fix processing of OOO commands

Fix two issues in OOO commands processing done at iscsit_attach_ooo_cmdsn.

Handle command serial numbers wrap around by using iscsi_sna_lt and not regular comparisson.

The routine iterates until it finds an entry whose serial number is greater than the serial number of
the new one, thus the new entry should be inserted before that entry and not after.

Signed-off-by: Shlomo Pongratz <shlomop@mellanox.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
rbd: fix leak of format 2 snapshot context

When rbd_dev_v2_refresh() is called, the rbd device already has a
snapshot context associated with it.  But that never gets freed,
the pointer just gets overwritten.

Fix this by dropping the rbd device's reference to the snapshot
context before overwriting the pointer.

Because ceph_put_snap_context() already handles for a null pointer
we don't need to check for that (for the probe case, where no
context has yet been assigned).

This resolves:
    http://tracker.ceph.com/issues/4912

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
rbd: revalidate only for mapping size changes

This commit:
    d98df63e rbd: revalidate_disk upon rbd resize
instituted a call to revalidate_disk() to notify interested parties
that a mapped image has changed size.  This works well, as long as
the the rbd device doesn't map a snapshot.

A snapshot will never change size.  However, the base image the
snapshot is associated with can, and it can do so while the snapshot
is mapped.

The problem is that the test for the size is looking at the size of
the base image, not the size of the mapped snapshot.  This patch
corrects that.

Update the warning message shown in the event of error, and move
it into the callers.

This resolves:
    http://tracker.ceph.com/issues/4911

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
rbd: update capacity in rbd_dev_refresh()

When a mapped image changes size, we change the capacity recorded
for the Linux disk associated with it, in rbd_update_mapping_size().
That function is called in two places--the format 1 and format 2
refresh routines.

There is no need to set the capacity while holding the header
semaphore.  Instead, do it in the common rbd_dev_refresh(), using
the logic that's already there to initiate disk revalidation.

Add handling in the request function, just in case a request
that exceeds the capacity of the device comes in (perhaps one
that was started before a refresh shrunk the device).

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>