There is a missing case for "Chapter 3: Placing Braces and Spaces". We
often know we should not use braces where a single statement. The first
case is:
if (condition)
action();
Another case is:
if (condition)
do_this();
else
do_that();
However, I can not find a description of the second case.
Signed-off-by: Harry Wei <harryxiyou@gmail.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When CONFIG_SYSCTL=n, we get the following warning:
fs/coda/sysctl.c:18: warning: `coda_tabl' defined but not used
Fix the warning by making sure coda_table and it's callee function are in
the same context. Also clean up the code by removing extra #ifdef.
[akpm@linux-foundation.org: remove unneeded stub macros]
Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com>
Cc: Jan Harkes <jaharkes@cs.cmu.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Not all 64-bit systems require ISA-style DMA, so allow it to be
configurable. x86 utilizes the generic ISA DMA allocator from
kernel/dma.c, so require it only when CONFIG_ISA_DMA_API is enabled.
Disabling CONFIG_ISA_DMA_API is dependent on x86_64 since those machines
do not have ISA slots and benefit the most from disabling the option (and
on CONFIG_EXPERT as required by H. Peter Anvin).
When disabled, this also avoids declaring claim_dma_lock(),
release_dma_lock(), request_dma(), and free_dma() since those interfaces
will no longer be provided.
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The generic floppy disk driver utilizies the interface provided by
CONFIG_ISA_DMA_API, specifically claim_dma_lock(), release_dma_lock(),
request_dma(), and free_dma(). Thus, there's a strict dependency on the
config option and the driver should only be loaded if the kernel supports
ISA-style DMA.
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
8237A utilizes the interface provided by CONFIG_ISA_DMA_API, specifically
claim_dma_lock() and release_dma_lock(). Thus, there's a strict
dependency on the config option and the module should only be loaded if
the kernel supports ISA-style DMA.
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
IORESOURCE_DMA cannot be assigned without utilizing the interface
provided by CONFIG_ISA_DMA_API, specifically request_dma() and
free_dma(). Thus, there's a strict dependency on the config option and
limits IORESOURCE_DMA only to architectures that support ISA-style DMA.
ia64 is not one of those architectures, so pnp_check_dma() no longer
needs to be special-cased for that architecture.
pnp_assign_resources() will now return -EINVAL if IORESOURCE_DMA is
attempted on such a kernel.
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is a platform driver that supports the built-in real-time clock on
Tegra SOCs.
Signed-off-by: Andrew Chew <achew@nvidia.com>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Acked-by: Wan ZongShun <mcuos.com@gmail.com>
Acked-by: Jon Mayo <jmayo@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is a general move to replace bus-specific PM ops with dev_pm_ops in
order to facilitate core improvements. Do this conversion for DS1374.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With GCC-4.6 we get warnings about things being 'set but not used'.
In load_elf_binary() this can happen with reloc_func_desc if ELF_PLAT_INIT
is defined, but doesn't use the reloc_func_desc argument.
Quiet the warning/error by marking reloc_func_desc as __maybe_unused.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add a comment to ep_poll(), rename labels a bit clearly, fix a warning of
unused variable from gcc and optimize the non-blocking path a little.
Hinted-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
hannes@cmpxchg.org:
: The non-blocking ep_poll path optimization introduced skipping over the
: return value setup.
:
: Initialize it properly, my userspace gets upset by epoll_wait() returning
: random things.
:
: In addition, remove the reinitialization at the fetch_events label, the
: return value is garuanteed to be zero when execution reaches there.
[hannes@cmpxchg.org: fix initialization]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shawn Bohrer <shawn.bohrer@gmail.com>
Acked-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Move the event readiness check into a proper inline, and use it uniformly
inside ep_poll() code. Events in the ->ovflist are no less ready than the
ones in ->rdllist.
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Shawn Bohrer <shawn.bohrer@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add brackets around typecasted argument in crc32() macro.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Because the second and third arguments of memset have the same type, it
turns out to be really easy to mix them up.
This bug comes up time after time, so checkpatch should really be checking
for it at patch submission time.
Signed-off-by: Dave Jones <davej@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If you run checkpatch against multiple patches, and one of them has a
whitespace issue which can be helped via a script (rpt_cleaners), you will
see the same NOTE over and over for all subsequent patches. It makes it
seem like those patches also have whitespace problems when in reality,
there's only one or two bad apples.
So reset rpt_cleaners back to 0 after we've issued the note so that it
only shows up near the patch with the actual problems.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Analog Devices' SigmaStudio can produce firmware blobs for devices with
these DSPs embedded (like some audio codecs). Allow these device drivers
to easily parse and load them.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1. simple_strto*() do not contain overflow checks and crufty,
libc way to indicate failure.
2. strict_strto*() also do not have overflow checks but the name and
comments pretend they do.
3. Both families have only "long long" and "long" variants,
but users want strtou8()
4. Both "simple" and "strict" prefixes are wrong:
Simple doesn't exactly say what's so simple, strict should not exist
because conversion should be strict by default.
The solution is to use "k" prefix and add convertors for more types.
Enter
kstrtoull()
kstrtoll()
kstrtoul()
kstrtol()
kstrtouint()
kstrtoint()
kstrtou64()
kstrtos64()
kstrtou32()
kstrtos32()
kstrtou16()
kstrtos16()
kstrtou8()
kstrtos8()
Include runtime testsuite (somewhat incomplete) as well.
strict_strto*() become deprecated, stubbed to kstrto*() and
eventually will be removed altogether.
Use kstrto*() in code today!
Note: on some archs _kstrtoul() and _kstrtol() are left in tree, even if
they'll be unused at runtime. This is temporarily solution,
because I don't want to hardcode list of archs where these
functions aren't needed. Current solution with sizeof() and
__alignof__ at least always works.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
And set the status to Orphan.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Jeroen Vreeken <pe1rxq@amsat.org>
Cc: Hans Verkuil <hverkuil@xs4all.nl>
Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
commit 937f961a65 ("x86: Move sfi to platform") moved the files, update
the pattern.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
commit 82e6923e18 ("ARM: lh7a40x: remove unmaintained platform support")
removed support, remove it from MAINTAINERS.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
commit 3b3da9d25a ("x86: Move scx200 to platform") moved it, convert the
pattern too.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
commit 66fa12c571 ("ieee1394: remove the old IEEE 1394 driver stack")
removed the code, remove the MAINTAINERS entry.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 52b661449a ("[media] rc: Rename remote controller type to rc_type
instead of ir_type") moved it around.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Maxim Levitsky <maximlevitsky@gmail.com>
Acked-by: Harry Wei <harryxiyou@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 6d803ba736 ("ARM: 6483/1: arm & sh: factorised duplicated
clkdev.c") moved it to a separate directory.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
CC'ing lkml is the default and doesn't need separate entries.
Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Harry Wei <harryxiyou@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Remove these patterns until such files are actually in the tree.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
wiki-analog doesn't seem to work, but wiki.analog does.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Typo in path.
Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add quotes around email address with periods and commas. So they don't
explode when pasted into certain email clients.
Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Harry Wei <harryxiyou@gmail.com>
Cc: "Mark F. Brown" <mark.brown314@gmail.com>
Cc: "Gustavo F. Padovan" <padovan@profusion.mobi>
Cc: "Stephen M. Cameron" <scameron@beardog.cce.hp.com>
Cc: "Lee, Chun-Yi" <jlee@novell.com>
Acked-by: Harry Wei <harryxiyou@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
At least one tree:
ARM/EZX SMARTPHONES (A780, A910, A1200, E680, ROKR E2 and ROKR E6)
is available via topgit. Add mention of topgit in the MAINTAINERS
description section.
Signed-off-by: Harry Wei <harryxiyou@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Extend the usage of the K section in the MAINTAINERS file to support
matching regular expressions to any arbitrary text that may precede the
patch itself. For example, the commit message or mail headers generated
by git-format-patch.
Signed-off-by: Joe Perches <joe@perches.com>
Original-patch-by: L. Alberto Giménez <agimenez@sysvalve.es>
Acked-by: L. Alberto Giménez <agimenez@sysvalve.es>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We've been burned by regressions/bugs which we later realized could have
been triaged quicker if only we'd paid closer attention to dmesg. To make
it easier to audit dmesg, we'd like to make DEFAULT_MESSAGE_LEVEL
Kconfig-settable. That way we can set it to KERN_NOTICE and audit any
messages <= KERN_WARNING.
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Joe Perches <joe@perches.com>
Cc: Olof Johansson <olofj@chromium.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In an effort to reduce kernel address leaks that might be used to help
target kernel privilege escalation exploits, this patch uses %pK when
displaying addresses in /proc/kallsyms, /proc/modules, and
/sys/module/*/sections/*.
Note that this changes %x to %p, so some legitimately 0 values in
/proc/kallsyms would have changed from 00000000 to "(null)". To avoid
this, "(null)" is not used when using the "K" format. Anything that was
already successfully parsing "(null)" in addition to full hex digits
should have no problem with this change. (Thanks to Joe Perches for the
suggestion.) Due to the %x to %p, "void *" casts are needed since these
addresses are already "unsigned long" everywhere internally, due to their
starting life as ELF section offsets.
Signed-off-by: Kees Cook <kees.cook@canonical.com>
Cc: Eugene Teo <eugene@redhat.com>
Cc: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
For a platform with many consoles like:
"console=tty1 console=ttyMFD2 console=ttyS0 earlyprintk=mrst"
Each time when the non "selected_console" (tty1 and ttyMFD2 here) get
registered, the existing kernel message will be printed out on registered
consoles again, the "mrst" early console will get some same message for 3
times, and "tty1" will get some for twice.
As suggested by Andrew Morton, every time a new console is registered, it
will be set as the "exclusive" console which will dump the already
existing kernel messages.
Signed-off-by: Feng Tang <feng.tang@intel.com>
Cc: Greg KH <gregkh@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
On some architectures, the boot process involves de-registering the boot
console (early boot), initialize drivers and then re-register the console.
This mechanism introduces a window in which no printk can happen on the
console and messages are buffered and then printed once the new console is
available.
If a kernel crashes during this window, all it's left on the boot console
is "console [foo] enabled, bootconsole disabled" making debug of the crash
rather 'interesting'.
By adding "keep_bootcon" option, do not unregister the boot console, that
will allow to printk everything that is happening up to the crash.
The option is clearly meant only for debugging purposes as it introduces
lots of duplicated info printed on console, but will make bug report from
users easier as it doesn't require a kernel build just to figure out where
we crash.
Signed-off-by: Fabio M. Di Nitto <fabbione@fabbione.net>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Greg KH <gregkh@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If kptr restrictions are on, just set the passed pointer to NULL.
$ size lib/vsprintf.o.*
text data bss dec hex filename
8247 4 2 8253 203d lib/vsprintf.o.new
8282 4 2 8288 2060 lib/vsprintf.o.old
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Dan Rosenberg <drosenberg@vsecurity.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch addresses a couple of problems. One was the case when the
hardlockup failed to start, it also failed to start the softlockup. There
were valid cases when the hardlockup shouldn't start and that shouldn't
block the softlockup (no lapic, bios controls perf counters).
The second problem was when the hardlockup failed to start on boxes (from
a no lapic or bios controlled perf counter case), it reported failure to
the cpu notifier chain. This blocked the notifier from continuing to
start other more critical pieces of cpu bring-up (in our case based on a
2.6.32 fork, it was the mce). As a result, during soft cpu online/offline
testing, the system would panic when a cpu was offlined because the cpu
notifier would succeed in processing a watchdog disable cpu event and
would panic in the mce case as a result of un-initialized variables from a
never executed cpu up event.
I realized the hardlockup/softlockup cases are really just debugging aids
and should never impede the progress of a cpu up/down event. Therefore I
modified the code to always return NOTIFY_OK and instead rely on printks
to inform the user of problems.
Signed-off-by: Don Zickus <dzickus@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When a cpu is considered stuck, instead of limping along and just printing
a warning, it is sometimes preferred to just panic, let kdump capture the
vmcore and reboot. This gets the machine back into a stable state quickly
while saving the info that got it into a stuck state to begin with.
Add a Kconfig option to allow users to set the hardlockup to panic
by default. Also add in a 'nmi_watchdog=nopanic' to override this.
[akpm@linux-foundation.org: fix strncmp length]
Signed-off-by: Don Zickus <dzickus@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Systems with unmaskable interrupts such as SMIs may massively
underestimate loops_per_jiffy, and fail to converge anywhere near the real
value. A case seen on x86_64 was an initial estimate of 256<<12, which
converged to 511<<12 where the real value should have been over 630<<12.
This admitedly requires bypassing the TSC calibration (lpj_fine), and a
failure to settle in the direct calibration too, but is physically
possible. This failure does not depend on my previous calibration
optimisation, but by luck is easy to fix with the optimisation in place
with a trivial retry loop.
In the context of the optimised converging method, as we can no longer
trust the starting estimate, enlarge the search bounds exponentially so
that the number of retries is logarithmically bounded.
[akpm@linux-foundation.org: mention x86_64 SMIs in comment]
Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Tested-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Binary chop with a jiffy-resync on each step to find an upper bound is
slow, so just race in a tight-ish loop to find an underestimate.
If done with lots of individual steps, sometimes several hundreds of
iterations would be required, which would impose a significant overhead,
and make the initial estimate very low. By taking slowly increasing steps
there will be less overhead.
E.g. an x86_64 2.67GHz could have fitted in 613 individual small delays,
but in reality should have been able to fit in a single delay 644 times
longer, so underestimated by 31 steps. To reach the equivalent of 644
small delays with the accelerating scheme now requires about 130
iterations, so has <1/4th of the overhead, and can therefore be expected
to underestimate by only 7 steps.
As now we have a better initial estimate we can binary chop over a smaller
range. With the loop overhead in the initial estimate kept low, and the
step sizes moderate, we won't have under-estimated by much, so chose as
tight a range as we can.
Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Tested-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The motivation for this patch series is that currently our OMAP calibrates
itself using the trial-and-error binary chop fallback that some other
architectures no longer need to perform. This is a lengthy process,
taking 0.2s in an environment where boot time is of great interest.
Patch 2/4 has two optimisations. Firstly, it replaces the initial
repeated- doubling to find the relevant power of 2 with a tight loop that
just does as much as it can in a jiffy. Secondly, it doesn't binary chop
over an entire power of 2 range, it choses a much smaller range based on
how much it squeezed in, and failed to squeeze in, during the first stage.
Both are significant optimisations, and bring our calibration down from
23 jiffies to 5, and, in the process, often arrive at a more accurate lpj
value.
The 'bands' and 'sub-logarithmic' growth may look over-engineered, but
they only cost a small level of inaccuracy in the initial guess (for all
architectures) in order to avoid the very large inaccuracies that appeared
during testing (on x86_64 architectures, and presumably others with less
metronomic operation). Note that due to the existence of the TSC and
other timers, the x86_64 will not typically use this fallback routine, but
I wanted to code defensively, able to cope with all kinds of processor
behaviours and kernel command line options.
Patch 3/4 is an additional trap for the nightmare scenario where the
initial estimate is very inaccurate, possibly due to things like SMIs.
It simply retries with a larger bound.
Stephen said:
I tried this patch set out on an MSM7630.
:
: Before:
:
: Calibrating delay loop... 681.57 BogoMIPS (lpj=3407872)
:
: After:
:
: Calibrating delay loop... 680.75 BogoMIPS (lpj=3403776)
:
: But the really good news is calibration time dropped from ~247ms to ~56ms.
: Sadly we won't be able to benefit from this should my udelay patches make
: it into ARM because we would be using calibrate_delay_direct() instead (at
: least on machines who choose to). Can we somehow reapply the logic behind
: this to calibrate_delay_direct()? That would be even better, but this is
: definitely a boot time improvement.
:
: Or maybe we could just replace calibrate_delay_direct() with this fallback
: calculation? If __delay() is a thin wrapper around read_current_timer()
: it should work just as well (plus patch 3 makes it handle SMIs). I'll try
: that out.
This patch:
... so that it can be modified more clinically.
This is almost entirely cosmetic. The only change to the operation
is that the global variable is only set once after the estimation is
completed, rather than taking on all the intermediate values. However,
there are no readers of that variable, so this change is unimportant.
Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Tested-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
