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  1. Mar 23, 2011
  3. Mar 21, 2011
  5. Mar 11, 2011
  7. Mar 08, 2011
    • Stanislaw Gruszka's avatar
      debugobjects: Add hint for better object identification · 99777288
      Stanislaw Gruszka authored 
      

In complex subsystems like mac80211 structures can contain several
timers and work structs, so identifying a specific instance from the
call trace and object type output of debugobjects can be hard.

Allow the subsystems which support debugobjects to provide a hint
function. This function returns a pointer to a kernel address
(preferrably the objects callback function) which is printed along
with the debugobjects type.

Add hint methods for timer_list, work_struct and hrtimer.

[ tglx: Massaged changelog, made it compile ]

Signed-off-by: default avatarStanislaw Gruszka <sgruszka@redhat.com>
LKML-Reference: <20110307085809.GA9334@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      99777288
  9. Mar 05, 2011
    • Arnd Bergmann's avatar
      BKL: That's all, folks · 4ba8216c
      Arnd Bergmann authored 
      

This removes the implementation of the big kernel lock,
at last. A lot of people have worked on this in the
past, I so the credit for this patch should be with
everyone who participated in the hunt.

The names on the Cc list are the people that were the
most active in this, according to the recorded git
history, in alphabetical order.

Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Acked-by: default avatarAlan Cox <alan@linux.intel.com>
Cc: Alessio Igor Bogani <abogani@texware.it>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Hendry <andrew.hendry@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Hans Verkuil <hverkuil@xs4all.nl>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Cc: Jan Blunck <jblunck@infradead.org>
Cc: John Kacur <jkacur@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Oliver Neukum <oliver@neukum.org>
Cc: Paul Menage <menage@google.com>
Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
      4ba8216c
  11. Mar 04, 2011
  13. Mar 01, 2011
  15. Feb 28, 2011
  17. Feb 25, 2011
  19. Feb 24, 2011
  21. Feb 18, 2011
    • Linus Torvalds's avatar
      Expand CONFIG_DEBUG_LIST to several other list operations · 3c18d4de
      Linus Torvalds authored 
      

When list debugging is enabled, we aim to readably show list corruption
errors, and the basic list_add/list_del operations end up having extra
debugging code in them to do some basic validation of the list entries.

However, "list_del_init()" and "list_move[_tail]()" ended up avoiding
the debug code due to how they were written. This fixes that.

So the _next_ time we have list_move() problems with stale list entries,
we'll hopefully have an easier time finding them..

Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      3c18d4de
  23. Feb 08, 2011
  25. Feb 03, 2011
  27. Jan 28, 2011
  29. Jan 27, 2011
    • Thomas Gleixner's avatar
      rwsem: Remove redundant asmregparm annotation · d1233754
      Thomas Gleixner authored 
      

Peter Zijlstra pointed out, that the only user of asmregparm (x86) is
compiling the kernel already with -mregparm=3. So the annotation of
the rwsem functions is redundant. Remove it.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: David Miller <davem@davemloft.net>
Cc: Chris Zankel <chris@zankel.net>
LKML-Reference: <alpine.LFD.2.00.1101262130450.31804@localhost6.localdomain6>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      d1233754
  31. Jan 26, 2011
    • Toshiyuki Okajima's avatar
      radix_tree: radix_tree_gang_lookup_tag_slot() may never return · ac15ee69
      Toshiyuki Okajima authored 
      

Executed command: fsstress -d /mnt -n 600 -p 850

  crash> bt
  PID: 7947   TASK: ffff880160546a70  CPU: 0   COMMAND: "fsstress"
   #0 [ffff8800dfc07d00] machine_kexec at ffffffff81030db9
   #1 [ffff8800dfc07d70] crash_kexec at ffffffff810a7952
   #2 [ffff8800dfc07e40] oops_end at ffffffff814aa7c8
   #3 [ffff8800dfc07e70] die_nmi at ffffffff814aa969
   #4 [ffff8800dfc07ea0] do_nmi_callback at ffffffff8102b07b
   #5 [ffff8800dfc07f10] do_nmi at ffffffff814aa514
   #6 [ffff8800dfc07f50] nmi at ffffffff814a9d60
      [exception RIP: __lookup_tag+100]
      RIP: ffffffff812274b4  RSP: ffff88016056b998  RFLAGS: 00000287
      RAX: 0000000000000000  RBX: 0000000000000002  RCX: 0000000000000006
      RDX: 000000000000001d  RSI: ffff88016056bb18  RDI: ffff8800c85366e0
      RBP: ffff88016056b9c8   R8: ffff88016056b9e8   R9: 0000000000000000
      R10: 000000000000000e  R11: ffff8800c8536908  R12: 0000000000000010
      R13: 0000000000000040  R14: ffffffffffffffc0  R15: ffff8800c85366e0
      ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
  <NMI exception stack>
   #7 [ffff88016056b998] __lookup_tag at ffffffff812274b4
   #8 [ffff88016056b9d0] radix_tree_gang_lookup_tag_slot at ffffffff81227605
   #9 [ffff88016056ba20] find_get_pages_tag at ffffffff810fc110
  #10 [ffff88016056ba80] pagevec_lookup_tag at ffffffff81105e85
  #11 [ffff88016056baa0] write_cache_pages at ffffffff81104c47
  #12 [ffff88016056bbd0] generic_writepages at ffffffff81105014
  #13 [ffff88016056bbe0] do_writepages at ffffffff81105055
  #14 [ffff88016056bbf0] __filemap_fdatawrite_range at ffffffff810fb2cb
  #15 [ffff88016056bc40] filemap_write_and_wait_range at ffffffff810fb32a
  #16 [ffff88016056bc70] generic_file_direct_write at ffffffff810fb3dc
  #17 [ffff88016056bce0] __generic_file_aio_write at ffffffff810fcee5
  #18 [ffff88016056bda0] generic_file_aio_write at ffffffff810fd085
  #19 [ffff88016056bdf0] do_sync_write at ffffffff8114f9ea
  #20 [ffff88016056bf00] vfs_write at ffffffff8114fcf8
  #21 [ffff88016056bf30] sys_write at ffffffff81150691
  #22 [ffff88016056bf80] system_call_fastpath at ffffffff8100c0b2

I think this root cause is the following:

 radix_tree_range_tag_if_tagged() always tags the root tag with settag
 if the root tag is set with iftag even if there are no iftag tags
 in the specified range (Of course, there are some iftag tags
 outside the specified range).

===============================================================================
[[[Detailed description]]]

(1) Why cannot radix_tree_gang_lookup_tag_slot() return forever?

__lookup_tag():
 - Return with 0.
 - Return with the index which is not bigger than the old one as the
   input parameter.

Therefore the following "while" repeats forever because the above
conditions cause "ret" not to be updated and the cur_index cannot be
changed into the bigger one.

(So, radix_tree_gang_lookup_tag_slot() cannot return forever.)

radix_tree_gang_lookup_tag_slot():
1178         while (ret < max_items) {
1179                 unsigned int slots_found;
1180                 unsigned long next_index;       /* Index of next search */
1181
1182                 if (cur_index > max_index)
1183                         break;
1184                 slots_found = __lookup_tag(node, results + ret,
1185                                 cur_index, max_items - ret, &next_index,
tag);
1186                 ret += slots_found;
			// cannot update ret because slots_found == 0.
			// so, this while loops forever.
1187                 if (next_index == 0)
1188                         break;
1189                 cur_index = next_index;
1190         }

(2) Why does __lookup_tag() return with 0 and doesn't update the index?

Assuming the following:
  - the one of the slot in radix_tree_node is NULL.
  - the one of the tag which corresponds to the slot sets with
    PAGECACHE_TAG_TOWRITE or other.
  - In a certain height(!=0), the corresponding index is 0.

a) __lookup_tag() notices that the tag is set.

1005 static unsigned int
1006 __lookup_tag(struct radix_tree_node *slot, void ***results, unsigned long index,
1007         unsigned int max_items, unsigned long *next_index, unsigned int tag)
1008 {
1009         unsigned int nr_found = 0;
1010         unsigned int shift, height;
1011
1012         height = slot->height;
1013         if (height == 0)
1014                 goto out;
1015         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
1016
1017         while (height > 0) {
1018                 unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK ;
1019
1020                 for (;;) {
1021                         if (tag_get(slot, tag, i))
1022                                 break;
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
* the index is not updated yet.

b) __lookup_tag() notices that the slot is NULL.

1023                         index &= ~((1UL << shift) - 1);
1024                         index += 1UL << shift;
1025                         if (index == 0)
1026                                 goto out;       /* 32-bit wraparound */
1027                         i++;
1028                         if (i == RADIX_TREE_MAP_SIZE)
1029                                 goto out;
1030                 }
1031                 height--;
1032                 if (height == 0) {      /* Bottom level: grab some items */
...
1055                 }
1056                 shift -= RADIX_TREE_MAP_SHIFT;
1057                 slot = rcu_dereference_raw(slot->slots[i]);
1058                 if (slot == NULL)
1059                         break;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

c) __lookup_tag() doesn't update the index and return with 0.

1060         }
1061 out:
1062         *next_index = index;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1063         return nr_found;
1064 }

(3) Why is the slot NULL even if the tag is set?

Because radix_tree_range_tag_if_tagged() always sets the root tag with
PAGECACHE_TAG_TOWRITE if the root tag is set with PAGECACHE_TAG_DIRTY,
even if there is no tag which can be set with PAGECACHE_TAG_TOWRITE
in the specified range (from *first_indexp to last_index). Of course,
some PAGECACHE_TAG_DIRTY nodes must exist outside the specified range.
(radix_tree_range_tag_if_tagged() is called only from tag_pages_for_writeback())

 640 unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root
*root,
 641                 unsigned long *first_indexp, unsigned long last_index,
 642                 unsigned long nr_to_tag,
 643                 unsigned int iftag, unsigned int settag)
 644 {
 645         unsigned int height = root->height;
 646         struct radix_tree_path path[height];
 647         struct radix_tree_path *pathp = path;
 648         struct radix_tree_node *slot;
 649         unsigned int shift;
 650         unsigned long tagged = 0;
 651         unsigned long index = *first_indexp;
 652
 653         last_index = min(last_index, radix_tree_maxindex(height));
 654         if (index > last_index)
 655                 return 0;
 656         if (!nr_to_tag)
 657                 return 0;
 658         if (!root_tag_get(root, iftag)) {
 659                 *first_indexp = last_index + 1;
 660                 return 0;
 661         }
 662         if (height == 0) {
 663                 *first_indexp = last_index + 1;
 664                 root_tag_set(root, settag);
 665                 return 1;
 666         }
...
 733         root_tag_set(root, settag);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 734         *first_indexp = index;
 735
 736         return tagged;
 737 }

As the result, there is no radix_tree_node which is set with
PAGECACHE_TAG_TOWRITE but the root tag(radix_tree_root) is set with
PAGECACHE_TAG_TOWRITE.

[figure: inside radix_tree]
(Please see the figure with typewriter font)
===========================================
          [roottag = DIRTY]
                 |             tag=0:NOTHING
         tag[0 0 0 1]              1:DIRTY
            [x x x +]              2:WRITEBACK
                   |               3:DIRTY,WRITEBACK
                   p               4:TOWRITE
             <--->                 5:DIRTY,TOWRITE ...
     specified range (index: 0 to 2)

* There is no DIRTY tag within the specified range.
 (But there is a DIRTY tag outside that range.)

            | | | | | | | | |
    after calling tag_pages_for_writeback()
            | | | | | | | | |
            v v v v v v v v v

          [roottag = DIRTY,TOWRITE]
                 |                 p is "page".
         tag[0 0 0 1]              x is NULL.
            [x x x +]              +- is a pointer to "page".
                   |
                   p

* But TOWRITE tag is set on the root tag.
============================================

After that, radix_tree_extend() via radix_tree_insert() is called
when the page is added.
This function sets the new radix_tree_node with PAGECACHE_TAG_TOWRITE
to succeed the status of the root tag.

 246 static int radix_tree_extend(struct radix_tree_root *root, unsigned long
index)
 247 {
 248         struct radix_tree_node *node;
 249         unsigned int height;
 250         int tag;
 251
 252         /* Figure out what the height should be.  */
 253         height = root->height + 1;
 254         while (index > radix_tree_maxindex(height))
 255                 height++;
 256
 257         if (root->rnode == NULL) {
 258                 root->height = height;
 259                 goto out;
 260         }
 261
 262         do {
 263                 unsigned int newheight;
 264                 if (!(node = radix_tree_node_alloc(root)))
 265                         return -ENOMEM;
 266
 267                 /* Increase the height.  */
 268                 node->slots[0] = radix_tree_indirect_to_ptr(root->rnode);
 269
 270                 /* Propagate the aggregated tag info into the new root */
 271                 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 272                         if (root_tag_get(root, tag))
 273                                 tag_set(node, tag, 0);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 274                 }

===========================================
          [roottag = DIRTY,TOWRITE]
                 |     :
         tag[0 0 0 1] [0 0 0 0]
            [x x x +] [+ x x x]
                   |   |
                   p   p (new page)

            | | | | | | | | |
    after calling radix_tree_insert
            | | | | | | | | |
            v v v v v v v v v

          [roottag = DIRTY,TOWRITE]
                 |
         tag [5 0 0 0]    *  DIRTY and TOWRITE tags are
             [+ + x x]       succeeded to the new node.
              | |
  tag [0 0 0 1] [0 0 0 0]
      [x x x +] [+ x x x]
             |   |
             p   p
============================================

After that, the index 3 page is released by remove_from_page_cache().
Then we can make the situation that the tag is set with PAGECACHE_TAG_TOWRITE
and that the slot which corresponds to the tag is NULL.
===========================================
          [roottag = DIRTY,TOWRITE]
                 |
         tag [5 0 0 0]
             [+ + x x]
              | |
  tag [0 0 0 1] [0 0 0 0]
      [x x x +] [+ x x x]
             |   |
             p   p
         (remove)

            | | | | | | | | |
    after calling remove_page_cache
            | | | | | | | | |
            v v v v v v v v v

          [roottag = DIRTY,TOWRITE]
                 |
         tag [4 0 0 0]      * Only DIRTY tag is cleared
             [x + x x]        because no TOWRITE tag is existed
                |             in the bottom node.
                [0 0 0 0]
                [+ x x x]
                 |
                 p
============================================

To solve this problem

Change to that radix_tree_tag_if_tagged() doesn't tag the root tag
if it doesn't set any tags within the specified range.

Like this.
============================================
 640 unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root
*root,
 641                 unsigned long *first_indexp, unsigned long last_index,
 642                 unsigned long nr_to_tag,
 643                 unsigned int iftag, unsigned int settag)
 644 {
 650         unsigned long tagged = 0;
...
 733 	     if (tagged)
^^^^^^^^^^^^^^^^^^^^^^^^
 734            root_tag_set(root, settag);
 735         *first_indexp = index;
 736
 737         return tagged;
 738 }

============================================

Signed-off-by: default avatarToshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Acked-by: default avatarJan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ac15ee69
  33. Jan 25, 2011
  35. Jan 24, 2011
  37. Jan 21, 2011
    • David Rientjes's avatar
      kconfig: rename CONFIG_EMBEDDED to CONFIG_EXPERT · 6a108a14
      David Rientjes authored 
      

The meaning of CONFIG_EMBEDDED has long since been obsoleted; the option
is used to configure any non-standard kernel with a much larger scope than
only small devices.

This patch renames the option to CONFIG_EXPERT in init/Kconfig and fixes
references to the option throughout the kernel.  A new CONFIG_EMBEDDED
option is added that automatically selects CONFIG_EXPERT when enabled and
can be used in the future to isolate options that should only be
considered for embedded systems (RISC architectures, SLOB, etc).

Calling the option "EXPERT" more accurately represents its intention: only
expert users who understand the impact of the configuration changes they
are making should enable it.

Reviewed-by: default avatarIngo Molnar <mingo@elte.hu>
Acked-by: default avatarDavid Woodhouse <david.woodhouse@intel.com>
Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
Cc: Greg KH <gregkh@suse.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Robin Holt <holt@sgi.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      6a108a14
  39. Jan 13, 2011