linux-toradex.git/kernel/cpu.c, branch v2.6.36.4

sched: adjust when cpu_active and cpuset configurations are updated during cpu on/offlining

2010-06-08T19:40:36+00:00

Currently, when a cpu goes down, cpu_active is cleared before
CPU_DOWN_PREPARE starts and cpuset configuration is updated from a
default priority cpu notifier.  When a cpu is coming up, it's set
before CPU_ONLINE but cpuset configuration again is updated from the
same cpu notifier.

For cpu notifiers, this presents an inconsistent state.  Threads which
a CPU_DOWN_PREPARE notifier expects to be bound to the CPU can be
migrated to other cpus because the cpu is no more inactive.

Fix it by updating cpu_active in the highest priority cpu notifier and
cpuset configuration in the second highest when a cpu is coming up.
Down path is updated similarly.  This guarantees that all other cpu
notifiers see consistent cpu_active and cpuset configuration.

cpuset_track_online_cpus() notifier is converted to
cpuset_update_active_cpus() which just updates the configuration and
now called from cpuset_cpu_[in]active() notifiers registered from
sched_init_smp().  If cpuset is disabled, cpuset_update_active_cpus()
degenerates into partition_sched_domains() making separate notifier
for !CONFIG_CPUSETS unnecessary.

This problem is triggered by cmwq.  During CPU_DOWN_PREPARE, hotplug
callback creates a kthread and kthread_bind()s it to the target cpu,
and the thread is expected to run on that cpu.

* Ingo's test discovered __cpuinit/exit markups were incorrect.
  Fixed.

Signed-off-by: Tejun Heo 
Acked-by: Peter Zijlstra 
Cc: Rusty Russell 
Cc: Ingo Molnar 
Cc: Paul Menage

fix cpu_chain section mismatch...

2010-06-01T16:22:50+00:00

In commit e9fb7631ebcd ("cpu-hotplug: introduce cpu_notify(),
__cpu_notify(), cpu_notify_nofail()") the new helper functions access
cpu_chain.  As a result, it shouldn't be marked __cpuinitdata (via
section mismatch warning).

Alternatively, the helper functions should be forced inline, or marked
__ref or __cpuinit.  In the meantime, this patch silences the warning
the trivial way.

Signed-off-by: Daniel J Blueman 
Signed-off-by: Linus Torvalds

CPU: Avoid using unititialized error variable in disable_nonboot_cpus()

2010-05-30T16:06:00+00:00

If there's only one CPU online when disable_nonboot_cpus() is called,
the error variable will not be initialized and that may lead to
erroneous behavior.  Fix this issue by initializing error in
disable_nonboot_cpus() as appropriate.

Signed-off-by: Rafael J. Wysocki 
Signed-off-by: Linus Torvalds

Avoid warning when CPU hotplug isn't enabled

2010-05-27T17:32:08+00:00

Commit e9fb7631ebcd ("cpu-hotplug: introduce cpu_notify(),
__cpu_notify(), cpu_notify_nofail()") also introduced this annoying
warning:

  kernel/cpu.c:157: warning: 'cpu_notify_nofail' defined but not used

when CONFIG_HOTPLUG_CPU wasn't set.

So move that helper inside the #ifdef CONFIG_HOTPLUG_CPU region, and
simplify it while at it.

Signed-off-by: Linus Torvalds

cpuhotplug: do not need cpu_hotplug_begin() when CONFIG_HOTPLUG_CPU=n

2010-05-27T16:12:48+00:00

Since when CONFIG_HOTPLUG_CPU=n, get_online_cpus() do nothing, so we don't
need cpu_hotplug_begin() either.

This patch moves cpu_hotplug_begin()/cpu_hotplug_done() into the code
block of CONFIG_HOTPLUG_CPU=y.

Signed-off-by: Lai Jiangshan 
Cc: Gautham R Shenoy 
Cc: Ingo Molnar 

Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

cpu-hotplug: return better errno on cpu hotplug failure

2010-05-27T16:12:47+00:00

Currently, onlining or offlining a CPU failure by one of the cpu notifiers
error always cause -EINVAL error.  (i.e.  writing 0 or 1 to
/sys/devices/system/cpu/cpuX/online gets EINVAL)

To get better error reporting rather than always getting -EINVAL, This
changes cpu_notify() to return -errno value with notifier_to_errno() and
fix the callers.  Now that cpu notifiers can return encapsulate errno
value.

Currently, all cpu hotplug notifiers return NOTIFY_OK, NOTIFY_BAD, or
NOTIFY_DONE.  So cpu_notify() can returns 0 or -EPERM with this change for
now.

(notifier_to_errno(NOTIFY_OK) == 0, notifier_to_errno(NOTIFY_DONE) == 0,
notifier_to_errno(NOTIFY_BAD) == -EPERM)

Forthcoming patches convert several cpu notifiers to return encapsulate
errno value with notifier_from_errno().

Signed-off-by: Akinobu Mita 
Cc: Rusty Russell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

cpu-hotplug: introduce cpu_notify(), __cpu_notify(), cpu_notify_nofail()

2010-05-27T16:12:47+00:00

No functional change.  These are just wrappers of
raw_cpu_notifier_call_chain.

Signed-off-by: Akinobu Mita 
Cc: Rusty Russell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mem-hotplug: fix potential race while building zonelist for new populated zone

2010-05-25T15:07:02+00:00

Add global mutex zonelists_mutex to fix the possible race:

     CPU0                                  CPU1                    CPU2
(1) zone->present_pages += online_pages;
(2)                                       build_all_zonelists();
(3)                                                               alloc_page();
(4)                                                               free_page();
(5) build_all_zonelists();
(6)   __build_all_zonelists();
(7)     zone->pageset = alloc_percpu();

In step (3,4), zone->pageset still points to boot_pageset, so bad
things may happen if 2+ nodes are in this state. Even if only 1 node
is accessing the boot_pageset, (3) may still consume too much memory
to fail the memory allocations in step (7).

Besides, atomic operation ensures alloc_percpu() in step (7) will never fail
since there is a new fresh memory block added in step(6).

[haicheng.li@linux.intel.com: hold zonelists_mutex when build_all_zonelists]
Signed-off-by: Haicheng Li 
Signed-off-by: Wu Fengguang 
Reviewed-by: Andi Kleen 
Cc: Christoph Lameter 
Cc: Mel Gorman 
Cc: Tejun Heo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mem-hotplug: avoid multiple zones sharing same boot strapping boot_pageset

2010-05-25T15:07:01+00:00

For each new populated zone of hotadded node, need to update its pagesets
with dynamically allocated per_cpu_pageset struct for all possible CPUs:

    1) Detach zone->pageset from the shared boot_pageset
       at end of __build_all_zonelists().

    2) Use mutex to protect zone->pageset when it's still
       shared in onlined_pages()

Otherwises, multiple zones of different nodes would share same boot strapping
boot_pageset for same CPU, which will finally cause below kernel panic:

  ------------[ cut here ]------------
  kernel BUG at mm/page_alloc.c:1239!
  invalid opcode: 0000 [#1] SMP
  ...
  Call Trace:
   [] __alloc_pages_nodemask+0x131/0x7b0
   [] alloc_pages_current+0x87/0xd0
   [] __page_cache_alloc+0x67/0x70
   [] __do_page_cache_readahead+0x120/0x260
   [] ra_submit+0x21/0x30
   [] ondemand_readahead+0x166/0x2c0
   [] page_cache_async_readahead+0x80/0xa0
   [] generic_file_aio_read+0x364/0x670
   [] nfs_file_read+0xca/0x130
   [] do_sync_read+0xfa/0x140
   [] vfs_read+0xb5/0x1a0
   [] sys_read+0x51/0x80
   [] system_call_fastpath+0x16/0x1b
  RIP  [] get_page_from_freelist+0x883/0x900
   RSP 
  ---[ end trace 4bda28328b9990db ]

[akpm@linux-foundation.org: merge fix]
Signed-off-by: Haicheng Li 
Signed-off-by: Wu Fengguang 
Reviewed-by: Andi Kleen 
Reviewed-by: Christoph Lameter 
Cc: Mel Gorman 
Cc: Tejun Heo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

cpu/mem hotplug: enable CPUs online before local memory online

2010-05-25T15:07:00+00:00

Enable users to online CPUs even if the CPUs belongs to a numa node which
doesn't have onlined local memory.

The zonlists(pg_data_t.node_zonelists[]) of a numa node are created either
in system boot/init period, or at the time of local memory online.  For a
numa node without onlined local memory, its zonelists are not initialized
at present.  As a result, any memory allocation operations executed by
CPUs within this node will fail.  In fact, an out-of-memory error is
triggered when attempt to online CPUs before memory comes to online.

This patch tries to create zonelists for such numa nodes, so that the
memory allocation for this node can be fallback'ed to other nodes.

[akpm@linux-foundation.org: remove unneeded export]
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: minskey guo
Cc: Minchan Kim 
Cc: Yasunori Goto 
Cc: Andi Kleen 
Cc: Christoph Lameter 
Cc: Tejun Heo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds