Commit Graph

448 Commits

Author SHA1 Message Date
Christoph Hellwig
6b9c7ed848 [PATCH] use ptrace_get_task_struct in various places
The ptrace_get_task_struct() helper that I added as part of the ptrace
consolidation is useful in variety of places that currently opencode it.
Switch them to the common helpers.

Add a ptrace_traceme() helper that needs to be explicitly called, and simplify
the ptrace_get_task_struct() interface.  We don't need the request argument
now, and we return the task_struct directly, using ERR_PTR() for error
returns.  It's a bit more code in the callers, but we have two sane routines
that do one thing well now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-08 20:13:51 -08:00
Christoph Lameter
39743889aa [PATCH] Swap Migration V5: sys_migrate_pages interface
sys_migrate_pages implementation using swap based page migration

This is the original API proposed by Ray Bryant in his posts during the first
half of 2005 on linux-mm@kvack.org and linux-kernel@vger.kernel.org.

The intent of sys_migrate is to migrate memory of a process.  A process may
have migrated to another node.  Memory was allocated optimally for the prior
context.  sys_migrate_pages allows to shift the memory to the new node.

sys_migrate_pages is also useful if the processes available memory nodes have
changed through cpuset operations to manually move the processes memory.  Paul
Jackson is working on an automated mechanism that will allow an automatic
migration if the cpuset of a process is changed.  However, a user may decide
to manually control the migration.

This implementation is put into the policy layer since it uses concepts and
functions that are also needed for mbind and friends.  The patch also provides
a do_migrate_pages function that may be useful for cpusets to automatically
move memory.  sys_migrate_pages does not modify policies in contrast to Ray's
implementation.

The current code here is based on the swap based page migration capability and
thus is not able to preserve the physical layout relative to it containing
nodeset (which may be a cpuset).  When direct page migration becomes available
then the implementation needs to be changed to do a isomorphic move of pages
between different nodesets.  The current implementation simply evicts all
pages in source nodeset that are not in the target nodeset.

Patch supports ia64, i386 and x86_64.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-08 20:12:42 -08:00
Tony Luck
38c0b2c2aa [IA64] Fix compile warnings in setup.c
arch/ia64/kernel/setup.c: In function `show_cpuinfo':
arch/ia64/kernel/setup.c:576: warning: long unsigned int format, different type arg (arg 12)
arch/ia64/kernel/setup.c:576: warning: long unsigned int format, different type arg (arg 13)

Introduced by 95235ca2c2

Signed-off-by: Tony Luck <tony.luck@intel.com>
2006-01-05 13:30:52 -08:00
Tony Luck
5c3eee7912 Auto-update from upstream 2006-01-05 08:52:11 -08:00
Linus Torvalds
db9edfd7e3 Merge git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-2.6
Trivial manual merge fixup for usb_find_interface clashes.
2006-01-04 18:44:12 -08:00
Linus Torvalds
0356dbb7fe Merge master.kernel.org:/pub/scm/linux/kernel/git/davej/cpufreq 2006-01-04 16:21:26 -08:00
Paul Jackson
6d20b035de [PATCH] driver kill hotplug word from sn and others fix
The first of these changes s/hotplug/uevent/ was needed to
compile sn2_defconfig (ia64/sn).  The other three files
changed are blind changes of all remaining bus_type.hotplug
references I could find to bus_type.uevent.

This patch attempts to finish similar changes made in the
gregkh-driver-kill-hotplug-word-from-driver-core Nov 22 patch.

Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2006-01-04 16:18:08 -08:00
Alex Williamson
408045afbd [IA64] incorrect return from ia64_pci_legacy_write()
The function ia64_pci_legacy_write() returns 0 for everything
except errors.  This return value gets sent back to the user from
pci_write_legacy_io(), making it look like every write fails.  The trivial
patch below copies the behavior of the SGI sn machvec and does what
would be expected from something implementing a write() function.

Signed-off-by: Alex Williamson <alex.williamson@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2006-01-03 11:16:17 -08:00
Christoph Lameter
dc86e88c2b [IA64] Add __read_mostly support for IA64
sparc64, i386 and x86_64 have support for a special data section dedicated
to rarely updated data that is frequently read. The section was created to
avoid false sharing of those rarely read data with frequently written kernel
data.

This patch creates such a data section for ia64 and will group rarely written
data into this section.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-12-16 10:52:46 -08:00
hawkes@sgi.com
d5bf3165b6 [IA64-SGI] change default_sn2 to NR_CPUS==1024
Change the NR_CPUS default for ia64/sn up to 1024.

Signed-off-by: John Hawkes <hawkes@sgi.com>
Signed-off-by: John Hesterberg <jh@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-12-16 10:51:29 -08:00
Jack Steiner
d74700e604 [IA64-SGI] Missed TLB flush
I see why the problem exists only on SN. SN uses a different hardware
mechanism to purge TLB entries across nodes.

It looks like there is a bug in the SN TLB flushing code. During context switch,
kernel threads inherit the mm of the task that was previously running on the
cpu. This confuses the code in sn2_global_tlb_purge().

The result is a missed TLB purge for the task that owns the "borrowed" mm.

(I hit the problem running heavy stress where kswapd was purging code pages of
a user task that woke kswapd. The user task took a SIGILL fault trying to
execute code in the page that had been ripped out from underneath it).

Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-12-16 10:46:25 -08:00
Jes Sorensen
3bd7f01713 [IA64] uncached ref count leak
Use raw_smp_processor_id() instead of get_cpu() as we don't need the
extra features of get_cpu().

Signed-off-by: Jes Sorensen <jes@trained-monkey.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-12-16 10:29:52 -08:00
John Hawkes
f5899b5d4f [IA64] disable preemption in udelay()
The udelay() inline for ia64 uses the ITC.  If CONFIG_PREEMPT is enabled
and the platform has unsynchronized ITCs and the calling task migrates
to another CPU while doing the udelay loop, then the effective delay may
be too short or very, very long.

This patch disables preemption around 100 usec chunks of the overall
desired udelay time.  This minimizes preemption-holdoffs.

udelay() is now too big to be inline, move it out of line and export it.

Signed-off-by: John Hawkes <hawkes@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-12-16 10:00:24 -08:00
Al Viro
b3e5b5b227 [PATCH] ia64 sn __iomem annotations
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-12-15 10:04:31 -08:00
Robin Holt
27af4cfd11 [IA64] fix for SET_PERSONALITY when CONFIG_IA32_SUPPORT is not set.
Missed this when fixing the SET_PERSONALITY change.

Signed-off-by: Robin Holt <holt@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-12-14 08:52:57 -08:00
Linus Torvalds
0e67050666 Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6 2005-12-12 16:48:29 -08:00
Yasunori Goto
ff9569bc55 [PATCH] Fix Kconfig of DMA32 for ia64
I realized ZONE_DMA32 has a trivial bug at Kconfig for ia64.  In
include/linux/gfp.h on 2.6.15-rc5-mm1, CONFIG is define like followings.

#ifdef CONFIG_DMA_IS_DMA32
#define __GFP_DMA32	((__force gfp_t)0x01)	/* ZONE_DMA is ZONE_DMA32
*/
       :
       :

So, CONFIG_"ZONE"_DMA_IS_DMA32 is clearly wrong.

Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-12-12 08:57:45 -08:00
Keshavamurthy Anil S
bf8d5c52c3 [PATCH] kprobes: increment kprobe missed count for multiprobes
When multiple probes are registered at the same address and if due to some
recursion (probe getting triggered within a probe handler), we skip calling
pre_handlers and just increment nmissed field.

The below patch make sure it walks the list for multiple probes case.
Without the below patch we get incorrect results of nmissed count for
multiple probe case.

Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-12-12 08:57:45 -08:00
Venkatesh Pallipadi
95235ca2c2 [CPUFREQ] CPU frequency display in /proc/cpuinfo
What is the value shown in "cpu MHz" of /proc/cpuinfo when CPUs are capable of
changing frequency?

Today the answer is: It depends.
On i386:
SMP kernel - It is always the boot frequency
UP kernel - Scales with the frequency change and shows that was last set.

On x86_64:
There is one single variable cpu_khz that gets written by all the CPUs. So,
the frequency set by last CPU will be seen on /proc/cpuinfo of all the
CPUs in the system. What you see also depends on whether you have constant_tsc
capable CPU or not.

On ia64:
It is always boot time frequency of a particular CPU that gets displayed.

The patch below changes this to:
Show the last known frequency of the particular CPU, when cpufreq is present. If
cpu doesnot support changing of frequency through cpufreq, then boot frequency
will be shown. The patch affects i386, x86_64 and ia64 architectures.

Signed-off-by: Venkatesh Pallipadi<venkatesh.pallipadi@intel.com>
Signed-off-by: Dave Jones <davej@redhat.com>
2005-12-06 19:35:11 -08:00
Jack Steiner
590711b7dd [IA64-SGI] Fix SN PTC deadlock recovery
The patch that added support for a new platform chipset (shub2) broke
PTC deadlock recovery on older versions of the chipset. (PTCs are the
SN platform-specific method for doing a global TLB purge). This
patch fixes deadlock recovery so that it works on both the old & new
chipsets.

Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-12-06 09:13:42 -08:00
Robin Holt
bd1d6e2451 [IA64] Change SET_PERSONALITY to comply with comment in binfmt_elf.c.
We have a customer application which trips a bug.  The problem arises
when a driver attempts to call do_munmap on an area which is mapped, but
because current->thread.task_size has been set to 0xC0000000, the call
to do_munmap fails thinking it is an unmap beyond the user's address
space.

The comment in fs/binfmt_elf.c in load_elf_library() before the call
to SET_PERSONALITY() indicates that task_size must not be changed for
the running application until flush_thread, but is for ia64 executing
ia32 binaries.

This patch moves the setting of task_size from SET_PERSONALITY() to
flush_thread() as indicated.  The customer application no longer is able
to trip the bug.

Signed-off-by: Robin Holt <holt@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-12-06 09:12:34 -08:00
Jack Steiner
acb7f67280 [IA64] Limit the maximum NODEDATA_ALIGN() offset
The per-node data structures are allocated with strided offsets that are a
function of the node number. This prevents excessive cache-aliasing from
occurring.

On systems with a large number of nodes, the strided offset becomes
too large. This patch restricts the maximum offset to 32MB. This is far larger
than the size of any current L3 cache.

Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-12-06 09:10:37 -08:00
John Keller
3ec829b689 [IA64-SGI] altix: pci_window fixup
Altix only patch to add fixup code that sets up
pci_controller->window. This code is a temporary
fix until ACPI support on Altix is added.

Also, corrects the usage of pci_dev->sysdata,
which had previously been used to reference
platform specific device info, to now point to
a pci_controller struct.

Signed-off-by: John Keller <jpk@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-12-06 09:09:23 -08:00
Keith Owens
05f70395c6 [IA64] Allow salinfo_decode to detect signals on read
Return -EINTR instead of -ERESTARTSYS when signals are delivered during
a blocked read of /proc/sal/*/event.  This allows salinfo_decode to
detect signals when it is blocked on a read of those files.

Signed-off-by: Keith Owens <kaos@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-12-05 11:49:17 -08:00
Tony Luck
885da19e80 [IA64] refresh tiger_defconfig ready for 2.6.15
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-12-02 16:18:42 -08:00
Robin Holt
1448652a54 [IA64] Updates to the sn2_defconfig for 2.6.15.
This updates the sn2_defconfig file for the Altix 330 hardware, enables
the AGP graphics for the SGI Prism, and removes prompts for the remainder
of the new features.  Greg Edwards reviewed the changes.

Signed-off-by: Robin Holt <holt@sgi.com>
Signed-off-by: Greg Edwards <edwardsg@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-12-02 13:32:44 -08:00
Keshavamurthy Anil S
5a94bcfd2a [IA64] Remove getting break_num by decoding instruction
break.b always sets cr.iim to 0 and the current code tries to
get the break_num by decoding instruction. However, their
seems to be a race condition while reading the regs->cr_iip,
as on other cpu the break.b at regs->cr_iip might have been
replaced with the original instruction as a result of
unregister_kprobe() and hence decoding instruction to
obtain break_num will result in wrong value in this case.

Also includes changes to kprobes.c which now has to handle
break number zero.

Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-11-29 09:24:39 -08:00
Dean Roe
b77dae5293 [IA64] - Make pfn_valid more precise for SGI Altix systems
A single SGI Altix system can be divided into multiple partitions,
each running their own instance of the Linux kernel.  pfn_valid()
is currently not optimal for any but the first partition, since it
does not compare the pfn with min_low_pfn before calling the more
costly ia64_pfn_valid().

Signed-off-by: Dean Roe <roe@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-11-29 09:24:10 -08:00
Jim Keniston
8bf1101bd5 [PATCH] kprobes: Fix return probes on sys_execve
Fix a bug in kprobes that can cause an Oops or even a crash when a return
probe is installed on one of the following functions: sys_execve,
do_execve, load_*_binary, flush_old_exec, or flush_thread.  The fix is to
remove the call to kprobe_flush_task() in flush_thread().  This fix has
been tested on all architectures for which the return-probes feature has
been implemented (i386, x86_64, ppc64, ia64).  Please apply.

BACKGROUND

Up to now, we have called kprobe_flush_task() under two situations: when a
task exits, and when it execs.  Flushing kretprobe_instances on exit is
correct because (a) do_exit() doesn't return, and (b) one or more
return-probed functions may be active when a task calls do_exit().  Neither
is the case for sys_execve() and its callees.

Initially, the mistaken call to kprobe_flush_task() on exec was harmless
because we put the "real" return address of each active probed function
back in the stack, just to be safe, when we recycled its
kretprobe_instance.  When support for ppc64 and ia64 was added, this safety
measure couldn't be employed, and was eventually dropped even for i386 and
x86_64.  sys_execve() and its callees were informally blacklisted for
return probes until this fix was developed.

Acked-by: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Signed-off-by: Jim Keniston <jkenisto@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-23 16:08:39 -08:00
Russ Anderson
ab2ff46a2d [IA64-SGI] bte_copy nasid_index fix
The nasid_index was not being incremented if the
pointer was null, causing an infinite loop.

Signed-off-by: Russ Anderson (rja@sgi.com)
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-11-21 14:19:36 -08:00
hawkes@sgi.com
090de0b77c [IA64] fix bug in sn/ia64 for sparse CPU numbering
The kernel's use of the for_each_*cpu(i) macros has allowed for sparse CPU
numbering.  When I hacked the kernel to test sparse cpu_present_map[] and
cpu_possible_map[] cpumasks, I discovered one remaining spot, in
sn_hwperf_ioctl() during sn initialization, that needs to be fixed.

Signed-off-by: John Hawkes <hawkes@sgi.com>
Signed-off-by: Dean Roe <roe@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-11-21 14:15:42 -08:00
Prarit Bhargava
9ad4f924ec [IA64] Prevent sn2 ptc code from executing on all ia64 subarches
Patch to prevent sn2_ptc_init code from attempting to load on non-sn2 systems
when sn2_smp.c is built-in to generic kernel.

Signed-off-by: Prarit Bhargava <prarit@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-11-21 14:13:31 -08:00
Chen, Kenneth W
e8aabc4716 [IA64] polish comments for tlb fault handler in ivt.S
Polish the comments specifically in vhpt_miss and nested_dtlb_miss
handlers.  I think it's better to explicitly name each page table
level with its name instead of numerically name them.  i.e., use
pgd, pud, pmd, and pte instead of referring as L1, L2, L3 etc.
Along the line, remove some magic number in the comments like:
"PTA + (((IFA(61,63) << 7) | IFA(33,39))*8)".  No code change at
all, pure comment update.  Feel free to shoot anything you have,
darts or tomahawk cruise missile.  I will duck behind a bunker ;-)

Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Acked-by: Robin Holt <holt@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-11-17 09:48:15 -08:00
Chen, Kenneth W
fedb25fae7 [IA64] 4 level page table bug fix in vhpt_miss
From source code inspection, I think there is a bug with 4 level
page table with vhpt_miss handler.  In the code path of rechecking
page table entry against previously read value after tlb insertion,
*pte value in register r18 was overwritten with value newly read
from pud pointer, render the check of new *pte against previous
*pte completely wrong.  Though the bug is none fatal and the penalty
is to purge the entry and retry.  For functional correctness, it
should be fixed.  The fix is to use a different register so new
*pud don't trash *pte.  (btw, the comments in the cmp statement is
wrong as well, which I will address in the next patch).

Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-11-17 09:47:18 -08:00
Chen, Kenneth W
1e185b97b4 [PATCH] ia64: cpu_idle performance bug fix
Our performance validation on 2.6.15-rc1 caught a disastrous performance
regression on ia64 with netperf (-98%) and volanomark (-58%) compares to
previous kernel version 2.6.14-git7.  See the following chart (result
group 1 & 2).

  http://kernel-perf.sourceforge.net/results.machine_id=26.html

We have root caused it to commit 64c7c8f885

This changeset broke the ia64 task resched notification.  In
sched.c:resched_task(), a reschedule IPI is conditioned upon
TIF_POLLING_NRFLAG.  However, the above changeset unconditionally set
the polling thread flag for idle tasks regardless whether pal_halt_light
is in use or not.  As a result, resched IPI is not sent from
resched_task().  And since the default behavior on ia64 is to use
pal_halt_light, we end up delaying the rescheduling task until next
timer tick, and thus cause the performance regression.

This fixes the performance bug.  I'm glad our performance suite is
turning up bad performance bug like this in time.

Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-15 15:50:51 -08:00
Linus Torvalds
4060994c3e Merge x86-64 update from Andi 2005-11-14 19:56:02 -08:00
Andi Kleen
d1e3dfdc2c [PATCH] x86_64: Set compatibility flag for 4GB zone on IA64
IA64 traditionally had a 4GB DMA32 zone. Set the compatibility flag
to keep old drivers working.

For new drivers it would be better to use ZONE_DMA32 now.

Cc: tony.luck@intel.com
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-14 19:55:13 -08:00
Mark Maule
ff51224cab [IA64-SGI] set altix preferred console
Fix default VGA console on SN platforms.  Since SN firmware does not pass
enough ACPI information to identify VGA cards and the associated legacy IO/MEM
addresses, we rely on the EFI PCDP table.  Since the linux pcdp driver is
optional (and overridden if console= directives are used) SN duplicates a
portion of the pcdp scan code to identify if there is a usable console VGA
adapter.  Additionally, dup necessary pcdp related structs to avoid dragging
drivers/pcdp.h into a more public location.

Signed-off-by: Mark Maule <maule@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-11-11 11:24:26 -08:00
Robin Holt
837cd0bdf5 [IA64] 4-level page tables
This patch introduces 4-level page tables to ia64.  I have run
some benchmarks and found nothing interesting.  Performance has
consistently fallen within the noise range.

It also introduces a config option (setting the default to 3
levels).  The config option prevents having 4 level page
tables with 64k base page size.

Signed-off-by: Robin Holt <holt@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-11-11 09:37:29 -08:00
Dean Nelson
780d09e895 [IA64] utilize notify_die() for XPC disengage
XPC (as in arch/ia64/sn/kernel/xp*) has a need to notify other partitions
(SGI Altix) whenever a partition is going down in order to get them to
disengage from accessing the halting partition's memory. If this is not
done before the reset of the hardware, the other partitions can find
themselves encountering MCAs that bring them down.

Signed-off-by: Dean Nelson <dcn@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-11-10 11:32:41 -08:00
Panagiotis Issaris
baf47fb660 [IA64] Replace kcalloc(1, with kzalloc.
Conversion from kcalloc(1, to kzalloc.

Signed-off-by: Panagiotis Issaris <takis@issaris.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2005-11-10 11:28:20 -08:00
Tony Luck
16e85d1a31 Pull add-mmio-to-proc-iomem into release branch 2005-11-10 10:40:32 -08:00
Tony Luck
7669a22592 Pull context-bitmap into release branch 2005-11-10 10:39:49 -08:00
Tony Luck
cb8a55e4cd Pull extend-notify-die into release branch 2005-11-10 10:39:09 -08:00
Tony Luck
4ddccb8eb9 Pull memoryless-node-allocation into release branch 2005-11-10 10:38:41 -08:00
Tony Luck
cf1d469ec1 Pull mca-check-psp into release branch 2005-11-10 10:38:05 -08:00
Tony Luck
64de57ffd3 Pull align-sig-frame into release branch 2005-11-10 10:37:35 -08:00
Linus Torvalds
7df446e7e0 Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6 2005-11-09 08:33:27 -08:00
Nick Piggin
64c7c8f885 [PATCH] sched: resched and cpu_idle rework
Make some changes to the NEED_RESCHED and POLLING_NRFLAG to reduce
confusion, and make their semantics rigid.  Improves efficiency of
resched_task and some cpu_idle routines.

* In resched_task:
- TIF_NEED_RESCHED is only cleared with the task's runqueue lock held,
  and as we hold it during resched_task, then there is no need for an
  atomic test and set there. The only other time this should be set is
  when the task's quantum expires, in the timer interrupt - this is
  protected against because the rq lock is irq-safe.

- If TIF_NEED_RESCHED is set, then we don't need to do anything. It
  won't get unset until the task get's schedule()d off.

- If we are running on the same CPU as the task we resched, then set
  TIF_NEED_RESCHED and no further action is required.

- If we are running on another CPU, and TIF_POLLING_NRFLAG is *not* set
  after TIF_NEED_RESCHED has been set, then we need to send an IPI.

Using these rules, we are able to remove the test and set operation in
resched_task, and make clear the previously vague semantics of
POLLING_NRFLAG.

* In idle routines:
- Enter cpu_idle with preempt disabled. When the need_resched() condition
  becomes true, explicitly call schedule(). This makes things a bit clearer
  (IMO), but haven't updated all architectures yet.

- Many do a test and clear of TIF_NEED_RESCHED for some reason. According
  to the resched_task rules, this isn't needed (and actually breaks the
  assumption that TIF_NEED_RESCHED is only cleared with the runqueue lock
  held). So remove that. Generally one less locked memory op when switching
  to the idle thread.

- Many idle routines clear TIF_POLLING_NRFLAG, and only set it in the inner
  most polling idle loops. The above resched_task semantics allow it to be
  set until before the last time need_resched() is checked before going into
  a halt requiring interrupt wakeup.

  Many idle routines simply never enter such a halt, and so POLLING_NRFLAG
  can be always left set, completely eliminating resched IPIs when rescheduling
  the idle task.

  POLLING_NRFLAG width can be increased, to reduce the chance of resched IPIs.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Con Kolivas <kernel@kolivas.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-09 07:56:33 -08:00
Nick Piggin
5bfb5d690f [PATCH] sched: disable preempt in idle tasks
Run idle threads with preempt disabled.

Also corrected a bugs in arm26's cpu_idle (make it actually call schedule()).
How did it ever work before?

Might fix the CPU hotplugging hang which Nigel Cunningham noted.

We think the bug hits if the idle thread is preempted after checking
need_resched() and before going to sleep, then the CPU offlined.

After calling stop_machine_run, the CPU eventually returns from preemption and
into the idle thread and goes to sleep.  The CPU will continue executing
previous idle and have no chance to call play_dead.

By disabling preemption until we are ready to explicitly schedule, this bug is
fixed and the idle threads generally become more robust.

From: alexs <ashepard@u.washington.edu>

  PPC build fix

From: Yoichi Yuasa <yuasa@hh.iij4u.or.jp>

  MIPS build fix

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Yoichi Yuasa <yuasa@hh.iij4u.or.jp>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-09 07:56:33 -08:00