<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux.git/kernel/locking/lockdep.c, branch v6.11-rc2</title>
<subtitle>Linux kernel source tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/'/>
<entry>
<title>Merge tag 'bcachefs-2024-07-18.2' of https://evilpiepirate.org/git/bcachefs</title>
<updated>2024-07-19T00:27:43+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2024-07-19T00:27:43+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=720261cfc7329406a50c2a8536e0039b9dd9a4e5'/>
<id>720261cfc7329406a50c2a8536e0039b9dd9a4e5</id>
<content type='text'>
Pull bcachefs updates from Kent Overstreet:

 - Metadata version 1.8: Stripe sectors accounting, BCH_DATA_unstriped

   This splits out the accounting of dirty sectors and stripe sectors in
   alloc keys; this lets us see stripe buckets that still have unstriped
   data in them.

   This is needed for ensuring that erasure coding is working correctly,
   as well as completing stripe creation after a crash.

 - Metadata version 1.9: Disk accounting rewrite

   The previous disk accounting scheme relied heavily on percpu counters
   that were also sharded by outstanding journal buffer; it was fast but
   not extensible or scalable, and meant that all accounting counters
   were recorded in every journal entry.

   The new disk accounting scheme stores accounting as normal btree
   keys; updates are deltas until they are flushed by the btree write
   buffer.

   This means we have no practical limit on the number of counters, and
   a new tagged union format that's easy to extend.

   We now have counters for compression type/ratio, per-snapshot-id
   usage, per-btree-id usage, and pending rebalance work.

 - Self healing on read IO/checksum error

   Data is now automatically rewritten if we get a read error and then a
   successful retry

 - Mount API conversion (thanks to Thomas Bertschinger)

 - Better lockdep coverage

   Previously, btree node locks were tracked individually by lockdep,
   like any other lock. But we may take _many_ btree node locks
   simultaneously, we easily blow through the limit of 48 locks that
   lockdep can track, leading to lockdep turning itself off.

   Tracking each btree node lock individually isn't really necessary
   since we have our own cycle detector for deadlock avoidance and
   centralized tracking of btree node locks, so we now have a single
   lockdep_map in btree_trans for "any btree nodes are locked".

 - Some more small incremental work towards online check_allocations

 - Lots more debugging improvements

 - Fixes, including:
    - undefined behaviour fixes, originally noted as breaking userspace
      LTO builds
    - fix a spurious warning in fsck_err, reported by Marcin
    - fix an integer overflow on trans-&gt;nr_updates, also reported by
      Marcin; this broke during deletion of highly fragmented indirect
      extents

* tag 'bcachefs-2024-07-18.2' of https://evilpiepirate.org/git/bcachefs: (120 commits)
  lockdep: Add comments for lockdep_set_no{validate,track}_class()
  bcachefs: Fix integer overflow on trans-&gt;nr_updates
  bcachefs: silence silly kdoc warning
  bcachefs: Fix fsck warning about btree_trans not passed to fsck error
  bcachefs: Add an error message for insufficient rw journal devs
  bcachefs: varint: Avoid left-shift of a negative value
  bcachefs: darray: Don't pass NULL to memcpy()
  bcachefs: Kill bch2_assert_btree_nodes_not_locked()
  bcachefs: Rename BCH_WRITE_DONE -&gt; BCH_WRITE_SUBMITTED
  bcachefs: __bch2_read(): call trans_begin() on every loop iter
  bcachefs: show none if label is not set
  bcachefs: drop packed, aligned from bkey_inode_buf
  bcachefs: btree node scan: fall back to comparing by journal seq
  bcachefs: Add lockdep support for btree node locks
  lockdep: lockdep_set_notrack_class()
  bcachefs: Improve copygc_wait_to_text()
  bcachefs: Convert clock code to u64s
  bcachefs: Improve startup message
  bcachefs: Self healing on read IO error
  bcachefs: Make read_only a mount option again, but hidden
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull bcachefs updates from Kent Overstreet:

 - Metadata version 1.8: Stripe sectors accounting, BCH_DATA_unstriped

   This splits out the accounting of dirty sectors and stripe sectors in
   alloc keys; this lets us see stripe buckets that still have unstriped
   data in them.

   This is needed for ensuring that erasure coding is working correctly,
   as well as completing stripe creation after a crash.

 - Metadata version 1.9: Disk accounting rewrite

   The previous disk accounting scheme relied heavily on percpu counters
   that were also sharded by outstanding journal buffer; it was fast but
   not extensible or scalable, and meant that all accounting counters
   were recorded in every journal entry.

   The new disk accounting scheme stores accounting as normal btree
   keys; updates are deltas until they are flushed by the btree write
   buffer.

   This means we have no practical limit on the number of counters, and
   a new tagged union format that's easy to extend.

   We now have counters for compression type/ratio, per-snapshot-id
   usage, per-btree-id usage, and pending rebalance work.

 - Self healing on read IO/checksum error

   Data is now automatically rewritten if we get a read error and then a
   successful retry

 - Mount API conversion (thanks to Thomas Bertschinger)

 - Better lockdep coverage

   Previously, btree node locks were tracked individually by lockdep,
   like any other lock. But we may take _many_ btree node locks
   simultaneously, we easily blow through the limit of 48 locks that
   lockdep can track, leading to lockdep turning itself off.

   Tracking each btree node lock individually isn't really necessary
   since we have our own cycle detector for deadlock avoidance and
   centralized tracking of btree node locks, so we now have a single
   lockdep_map in btree_trans for "any btree nodes are locked".

 - Some more small incremental work towards online check_allocations

 - Lots more debugging improvements

 - Fixes, including:
    - undefined behaviour fixes, originally noted as breaking userspace
      LTO builds
    - fix a spurious warning in fsck_err, reported by Marcin
    - fix an integer overflow on trans-&gt;nr_updates, also reported by
      Marcin; this broke during deletion of highly fragmented indirect
      extents

* tag 'bcachefs-2024-07-18.2' of https://evilpiepirate.org/git/bcachefs: (120 commits)
  lockdep: Add comments for lockdep_set_no{validate,track}_class()
  bcachefs: Fix integer overflow on trans-&gt;nr_updates
  bcachefs: silence silly kdoc warning
  bcachefs: Fix fsck warning about btree_trans not passed to fsck error
  bcachefs: Add an error message for insufficient rw journal devs
  bcachefs: varint: Avoid left-shift of a negative value
  bcachefs: darray: Don't pass NULL to memcpy()
  bcachefs: Kill bch2_assert_btree_nodes_not_locked()
  bcachefs: Rename BCH_WRITE_DONE -&gt; BCH_WRITE_SUBMITTED
  bcachefs: __bch2_read(): call trans_begin() on every loop iter
  bcachefs: show none if label is not set
  bcachefs: drop packed, aligned from bkey_inode_buf
  bcachefs: btree node scan: fall back to comparing by journal seq
  bcachefs: Add lockdep support for btree node locks
  lockdep: lockdep_set_notrack_class()
  bcachefs: Improve copygc_wait_to_text()
  bcachefs: Convert clock code to u64s
  bcachefs: Improve startup message
  bcachefs: Self healing on read IO error
  bcachefs: Make read_only a mount option again, but hidden
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>lockdep: lockdep_set_notrack_class()</title>
<updated>2024-07-14T23:00:16+00:00</updated>
<author>
<name>Kent Overstreet</name>
<email>kent.overstreet@linux.dev</email>
</author>
<published>2023-12-22T01:34:17+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=1a616c2fe96b357894b74b41787d4ea6987f6199'/>
<id>1a616c2fe96b357894b74b41787d4ea6987f6199</id>
<content type='text'>
Add a new helper to disable lockdep tracking entirely for a given class.

This is needed for bcachefs, which takes too many btree node locks for
lockdep to track. Instead, we have a single lockdep_map for "btree_trans
has any btree nodes locked", which makes more since given that we have
centralized lock management and a cycle detector.

Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Ingo Molnar &lt;mingo@redhat.com&gt;
Cc: Will Deacon &lt;will@kernel.org&gt;
Cc: Waiman Long &lt;longman@redhat.com&gt;
Cc: Boqun Feng &lt;boqun.feng@gmail.com&gt;
Signed-off-by: Kent Overstreet &lt;kent.overstreet@linux.dev&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Add a new helper to disable lockdep tracking entirely for a given class.

This is needed for bcachefs, which takes too many btree node locks for
lockdep to track. Instead, we have a single lockdep_map for "btree_trans
has any btree nodes locked", which makes more since given that we have
centralized lock management and a cycle detector.

Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Ingo Molnar &lt;mingo@redhat.com&gt;
Cc: Will Deacon &lt;will@kernel.org&gt;
Cc: Waiman Long &lt;longman@redhat.com&gt;
Cc: Boqun Feng &lt;boqun.feng@gmail.com&gt;
Signed-off-by: Kent Overstreet &lt;kent.overstreet@linux.dev&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>locking: Remove superfluous sentinel element from kern_lockdep_table</title>
<updated>2024-06-13T08:50:52+00:00</updated>
<author>
<name>Joel Granados</name>
<email>j.granados@samsung.com</email>
</author>
<published>2024-06-04T06:29:19+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=2f7c6248920523ca7468711891aa13f80ede8da4'/>
<id>2f7c6248920523ca7468711891aa13f80ede8da4</id>
<content type='text'>
This commit is part of a greater effort to remove all
empty elements at the end of the ctl_table arrays (sentinels) which will
reduce the overall build time size of the kernel and run time memory
bloat by ~64 bytes per sentinel (further information Link :
https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)

Signed-off-by: Joel Granados &lt;j.granados@samsung.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This commit is part of a greater effort to remove all
empty elements at the end of the ctl_table arrays (sentinels) which will
reduce the overall build time size of the kernel and run time memory
bloat by ~64 bytes per sentinel (further information Link :
https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)

Signed-off-by: Joel Granados &lt;j.granados@samsung.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>lockdep: Fix block chain corruption</title>
<updated>2023-11-24T10:04:54+00:00</updated>
<author>
<name>Peter Zijlstra</name>
<email>peterz@infradead.org</email>
</author>
<published>2023-11-21T11:41:26+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=bca4104b00fec60be330cd32818dd5c70db3d469'/>
<id>bca4104b00fec60be330cd32818dd5c70db3d469</id>
<content type='text'>
Kent reported an occasional KASAN splat in lockdep. Mark then noted:

&gt; I suspect the dodgy access is to chain_block_buckets[-1], which hits the last 4
&gt; bytes of the redzone and gets (incorrectly/misleadingly) attributed to
&gt; nr_large_chain_blocks.

That would mean @size == 0, at which point size_to_bucket() returns -1
and the above happens.

alloc_chain_hlocks() has 'size - req', for the first with the
precondition 'size &gt;= rq', which allows the 0.

This code is trying to split a block, del_chain_block() takes what we
need, and add_chain_block() puts back the remainder, except in the
above case the remainder is 0 sized and things go sideways.

Fixes: 810507fe6fd5 ("locking/lockdep: Reuse freed chain_hlocks entries")
Reported-by: Kent Overstreet &lt;kent.overstreet@linux.dev&gt;
Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Tested-by: Kent Overstreet &lt;kent.overstreet@linux.dev&gt;
Link: https://lkml.kernel.org/r/20231121114126.GH8262@noisy.programming.kicks-ass.net
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Kent reported an occasional KASAN splat in lockdep. Mark then noted:

&gt; I suspect the dodgy access is to chain_block_buckets[-1], which hits the last 4
&gt; bytes of the redzone and gets (incorrectly/misleadingly) attributed to
&gt; nr_large_chain_blocks.

That would mean @size == 0, at which point size_to_bucket() returns -1
and the above happens.

alloc_chain_hlocks() has 'size - req', for the first with the
precondition 'size &gt;= rq', which allows the 0.

This code is trying to split a block, del_chain_block() takes what we
need, and add_chain_block() puts back the remainder, except in the
above case the remainder is 0 sized and things go sideways.

Fixes: 810507fe6fd5 ("locking/lockdep: Reuse freed chain_hlocks entries")
Reported-by: Kent Overstreet &lt;kent.overstreet@linux.dev&gt;
Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Tested-by: Kent Overstreet &lt;kent.overstreet@linux.dev&gt;
Link: https://lkml.kernel.org/r/20231121114126.GH8262@noisy.programming.kicks-ass.net
</pre>
</div>
</content>
</entry>
<entry>
<title>lockdep: fix static memory detection even more</title>
<updated>2023-08-21T20:46:24+00:00</updated>
<author>
<name>Helge Deller</name>
<email>deller@gmx.de</email>
</author>
<published>2023-08-14T22:31:09+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=0a6b58c5cd0dfd7961e725212f0fc8dfc5d96195'/>
<id>0a6b58c5cd0dfd7961e725212f0fc8dfc5d96195</id>
<content type='text'>
On the parisc architecture, lockdep reports for all static objects which
are in the __initdata section (e.g. "setup_done" in devtmpfs,
"kthreadd_done" in init/main.c) this warning:

	INFO: trying to register non-static key.

The warning itself is wrong, because those objects are in the __initdata
section, but the section itself is on parisc outside of range from
_stext to _end, which is why the static_obj() functions returns a wrong
answer.

While fixing this issue, I noticed that the whole existing check can
be simplified a lot.
Instead of checking against the _stext and _end symbols (which include
code areas too) just check for the .data and .bss segments (since we check a
data object). This can be done with the existing is_kernel_core_data()
macro.

In addition objects in the __initdata section can be checked with
init_section_contains(), and is_kernel_rodata() allows keys to be in the
_ro_after_init section.

This partly reverts and simplifies commit bac59d18c701 ("x86/setup: Fix static
memory detection").

Link: https://lkml.kernel.org/r/ZNqrLRaOi/3wPAdp@p100
Fixes: bac59d18c701 ("x86/setup: Fix static memory detection")
Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Cc: Borislav Petkov &lt;bp@suse.de&gt;
Cc: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
Cc: Guenter Roeck &lt;linux@roeck-us.net&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: "Rafael J. Wysocki" &lt;rafael@kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
On the parisc architecture, lockdep reports for all static objects which
are in the __initdata section (e.g. "setup_done" in devtmpfs,
"kthreadd_done" in init/main.c) this warning:

	INFO: trying to register non-static key.

The warning itself is wrong, because those objects are in the __initdata
section, but the section itself is on parisc outside of range from
_stext to _end, which is why the static_obj() functions returns a wrong
answer.

While fixing this issue, I noticed that the whole existing check can
be simplified a lot.
Instead of checking against the _stext and _end symbols (which include
code areas too) just check for the .data and .bss segments (since we check a
data object). This can be done with the existing is_kernel_core_data()
macro.

In addition objects in the __initdata section can be checked with
init_section_contains(), and is_kernel_rodata() allows keys to be in the
_ro_after_init section.

This partly reverts and simplifies commit bac59d18c701 ("x86/setup: Fix static
memory detection").

Link: https://lkml.kernel.org/r/ZNqrLRaOi/3wPAdp@p100
Fixes: bac59d18c701 ("x86/setup: Fix static memory detection")
Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
Cc: Borislav Petkov &lt;bp@suse.de&gt;
Cc: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
Cc: Guenter Roeck &lt;linux@roeck-us.net&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: "Rafael J. Wysocki" &lt;rafael@kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'locking-core-2023-06-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip</title>
<updated>2023-06-27T21:14:30+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2023-06-27T21:14:30+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=bc6cb4d5bc3a44197de30784eae71d8ba28483eb'/>
<id>bc6cb4d5bc3a44197de30784eae71d8ba28483eb</id>
<content type='text'>
Pull locking updates from Ingo Molnar:

 - Introduce cmpxchg128() -- aka. the demise of cmpxchg_double()

   The cmpxchg128() family of functions is basically &amp; functionally the
   same as cmpxchg_double(), but with a saner interface.

   Instead of a 6-parameter horror that forced u128 - u64/u64-halves
   layout details on the interface and exposed users to complexity,
   fragility &amp; bugs, use a natural 3-parameter interface with u128
   types.

 - Restructure the generated atomic headers, and add kerneldoc comments
   for all of the generic atomic{,64,_long}_t operations.

   The generated definitions are much cleaner now, and come with
   documentation.

 - Implement lock_set_cmp_fn() on lockdep, for defining an ordering when
   taking multiple locks of the same type.

   This gets rid of one use of lockdep_set_novalidate_class() in the
   bcache code.

 - Fix raw_cpu_generic_try_cmpxchg() bug due to an unintended variable
   shadowing generating garbage code on Clang on certain ARM builds.

* tag 'locking-core-2023-06-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (43 commits)
  locking/atomic: scripts: fix ${atomic}_dec_if_positive() kerneldoc
  percpu: Fix self-assignment of __old in raw_cpu_generic_try_cmpxchg()
  locking/atomic: treewide: delete arch_atomic_*() kerneldoc
  locking/atomic: docs: Add atomic operations to the driver basic API documentation
  locking/atomic: scripts: generate kerneldoc comments
  docs: scripts: kernel-doc: accept bitwise negation like ~@var
  locking/atomic: scripts: simplify raw_atomic*() definitions
  locking/atomic: scripts: simplify raw_atomic_long*() definitions
  locking/atomic: scripts: split pfx/name/sfx/order
  locking/atomic: scripts: restructure fallback ifdeffery
  locking/atomic: scripts: build raw_atomic_long*() directly
  locking/atomic: treewide: use raw_atomic*_&lt;op&gt;()
  locking/atomic: scripts: add trivial raw_atomic*_&lt;op&gt;()
  locking/atomic: scripts: factor out order template generation
  locking/atomic: scripts: remove leftover "${mult}"
  locking/atomic: scripts: remove bogus order parameter
  locking/atomic: xtensa: add preprocessor symbols
  locking/atomic: x86: add preprocessor symbols
  locking/atomic: sparc: add preprocessor symbols
  locking/atomic: sh: add preprocessor symbols
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull locking updates from Ingo Molnar:

 - Introduce cmpxchg128() -- aka. the demise of cmpxchg_double()

   The cmpxchg128() family of functions is basically &amp; functionally the
   same as cmpxchg_double(), but with a saner interface.

   Instead of a 6-parameter horror that forced u128 - u64/u64-halves
   layout details on the interface and exposed users to complexity,
   fragility &amp; bugs, use a natural 3-parameter interface with u128
   types.

 - Restructure the generated atomic headers, and add kerneldoc comments
   for all of the generic atomic{,64,_long}_t operations.

   The generated definitions are much cleaner now, and come with
   documentation.

 - Implement lock_set_cmp_fn() on lockdep, for defining an ordering when
   taking multiple locks of the same type.

   This gets rid of one use of lockdep_set_novalidate_class() in the
   bcache code.

 - Fix raw_cpu_generic_try_cmpxchg() bug due to an unintended variable
   shadowing generating garbage code on Clang on certain ARM builds.

* tag 'locking-core-2023-06-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (43 commits)
  locking/atomic: scripts: fix ${atomic}_dec_if_positive() kerneldoc
  percpu: Fix self-assignment of __old in raw_cpu_generic_try_cmpxchg()
  locking/atomic: treewide: delete arch_atomic_*() kerneldoc
  locking/atomic: docs: Add atomic operations to the driver basic API documentation
  locking/atomic: scripts: generate kerneldoc comments
  docs: scripts: kernel-doc: accept bitwise negation like ~@var
  locking/atomic: scripts: simplify raw_atomic*() definitions
  locking/atomic: scripts: simplify raw_atomic_long*() definitions
  locking/atomic: scripts: split pfx/name/sfx/order
  locking/atomic: scripts: restructure fallback ifdeffery
  locking/atomic: scripts: build raw_atomic_long*() directly
  locking/atomic: treewide: use raw_atomic*_&lt;op&gt;()
  locking/atomic: scripts: add trivial raw_atomic*_&lt;op&gt;()
  locking/atomic: scripts: factor out order template generation
  locking/atomic: scripts: remove leftover "${mult}"
  locking/atomic: scripts: remove bogus order parameter
  locking/atomic: xtensa: add preprocessor symbols
  locking/atomic: x86: add preprocessor symbols
  locking/atomic: sparc: add preprocessor symbols
  locking/atomic: sh: add preprocessor symbols
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'core-debugobjects-2023-05-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip</title>
<updated>2023-05-28T11:15:33+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2023-05-28T11:15:33+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=d8f14b84fefd8669cbcbe4fee3f61a44be904993'/>
<id>d8f14b84fefd8669cbcbe4fee3f61a44be904993</id>
<content type='text'>
Pull debugobjects fixes from Thomas Gleixner:
 "Two fixes for debugobjects:

   - Prevent the allocation path from waking up kswapd.

     That's a long standing issue due to the GFP_ATOMIC allocation flag.
     As debug objects can be invoked from pretty much any context waking
     kswapd can end up in arbitrary lock chains versus the waitqueue
     lock

   - Correct the explicit lockdep wait-type violation in
     debug_object_fill_pool()"

* tag 'core-debugobjects-2023-05-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  debugobjects: Don't wake up kswapd from fill_pool()
  debugobjects,locking: Annotate debug_object_fill_pool() wait type violation
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull debugobjects fixes from Thomas Gleixner:
 "Two fixes for debugobjects:

   - Prevent the allocation path from waking up kswapd.

     That's a long standing issue due to the GFP_ATOMIC allocation flag.
     As debug objects can be invoked from pretty much any context waking
     kswapd can end up in arbitrary lock chains versus the waitqueue
     lock

   - Correct the explicit lockdep wait-type violation in
     debug_object_fill_pool()"

* tag 'core-debugobjects-2023-05-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  debugobjects: Don't wake up kswapd from fill_pool()
  debugobjects,locking: Annotate debug_object_fill_pool() wait type violation
</pre>
</div>
</content>
</entry>
<entry>
<title>lockdep: Add lock_set_cmp_fn() annotation</title>
<updated>2023-05-19T10:35:10+00:00</updated>
<author>
<name>Kent Overstreet</name>
<email>kent.overstreet@linux.dev</email>
</author>
<published>2023-05-09T19:58:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=eb1cfd09f788e39948a82be8063e54e40dd018d9'/>
<id>eb1cfd09f788e39948a82be8063e54e40dd018d9</id>
<content type='text'>
This implements a new interface to lockdep, lock_set_cmp_fn(), for
defining a custom ordering when taking multiple locks of the same
class.

This is an alternative to subclasses, but can not fully replace them
since subclasses allow lock hierarchies with other clasees
inter-twined, while this relies on pure class nesting.

Specifically, if A is our nesting class then:

  A/0 &lt;- B &lt;- A/1

Would be a valid lock order with subclasses (each subclass really is a
full class from the validation PoV) but not with this annotation,
which requires all nesting to be consecutive.

Example output:

| ============================================
| WARNING: possible recursive locking detected
| 6.2.0-rc8-00003-g7d81e591ca6a-dirty #15 Not tainted
| --------------------------------------------
| kworker/14:3/938 is trying to acquire lock:
| ffff8880143218c8 (&amp;b-&gt;lock l=0 0:2803368){++++}-{3:3}, at: bch_btree_node_get.part.0+0x81/0x2b0
|
| but task is already holding lock:
| ffff8880143de8c8 (&amp;b-&gt;lock l=1 1048575:9223372036854775807){++++}-{3:3}, at: __bch_btree_map_nodes+0xea/0x1e0
| and the lock comparison function returns 1:
|
| other info that might help us debug this:
|  Possible unsafe locking scenario:
|
|        CPU0
|        ----
|   lock(&amp;b-&gt;lock l=1 1048575:9223372036854775807);
|   lock(&amp;b-&gt;lock l=0 0:2803368);
|
|  *** DEADLOCK ***
|
|  May be due to missing lock nesting notation
|
| 3 locks held by kworker/14:3/938:
|  #0: ffff888005ea9d38 ((wq_completion)bcache){+.+.}-{0:0}, at: process_one_work+0x1ec/0x530
|  #1: ffff8880098c3e70 ((work_completion)(&amp;cl-&gt;work)#3){+.+.}-{0:0}, at: process_one_work+0x1ec/0x530
|  #2: ffff8880143de8c8 (&amp;b-&gt;lock l=1 1048575:9223372036854775807){++++}-{3:3}, at: __bch_btree_map_nodes+0xea/0x1e0

[peterz: extended changelog]
Signed-off-by: Kent Overstreet &lt;kent.overstreet@linux.dev&gt;
Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Link: https://lkml.kernel.org/r/20230509195847.1745548-1-kent.overstreet@linux.dev
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This implements a new interface to lockdep, lock_set_cmp_fn(), for
defining a custom ordering when taking multiple locks of the same
class.

This is an alternative to subclasses, but can not fully replace them
since subclasses allow lock hierarchies with other clasees
inter-twined, while this relies on pure class nesting.

Specifically, if A is our nesting class then:

  A/0 &lt;- B &lt;- A/1

Would be a valid lock order with subclasses (each subclass really is a
full class from the validation PoV) but not with this annotation,
which requires all nesting to be consecutive.

Example output:

| ============================================
| WARNING: possible recursive locking detected
| 6.2.0-rc8-00003-g7d81e591ca6a-dirty #15 Not tainted
| --------------------------------------------
| kworker/14:3/938 is trying to acquire lock:
| ffff8880143218c8 (&amp;b-&gt;lock l=0 0:2803368){++++}-{3:3}, at: bch_btree_node_get.part.0+0x81/0x2b0
|
| but task is already holding lock:
| ffff8880143de8c8 (&amp;b-&gt;lock l=1 1048575:9223372036854775807){++++}-{3:3}, at: __bch_btree_map_nodes+0xea/0x1e0
| and the lock comparison function returns 1:
|
| other info that might help us debug this:
|  Possible unsafe locking scenario:
|
|        CPU0
|        ----
|   lock(&amp;b-&gt;lock l=1 1048575:9223372036854775807);
|   lock(&amp;b-&gt;lock l=0 0:2803368);
|
|  *** DEADLOCK ***
|
|  May be due to missing lock nesting notation
|
| 3 locks held by kworker/14:3/938:
|  #0: ffff888005ea9d38 ((wq_completion)bcache){+.+.}-{0:0}, at: process_one_work+0x1ec/0x530
|  #1: ffff8880098c3e70 ((work_completion)(&amp;cl-&gt;work)#3){+.+.}-{0:0}, at: process_one_work+0x1ec/0x530
|  #2: ffff8880143de8c8 (&amp;b-&gt;lock l=1 1048575:9223372036854775807){++++}-{3:3}, at: __bch_btree_map_nodes+0xea/0x1e0

[peterz: extended changelog]
Signed-off-by: Kent Overstreet &lt;kent.overstreet@linux.dev&gt;
Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Link: https://lkml.kernel.org/r/20230509195847.1745548-1-kent.overstreet@linux.dev
</pre>
</div>
</content>
</entry>
<entry>
<title>debugobjects,locking: Annotate debug_object_fill_pool() wait type violation</title>
<updated>2023-05-02T12:48:14+00:00</updated>
<author>
<name>Peter Zijlstra</name>
<email>peterz@infradead.org</email>
</author>
<published>2023-04-25T15:03:13+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=0cce06ba859a515bd06224085d3addb870608b6d'/>
<id>0cce06ba859a515bd06224085d3addb870608b6d</id>
<content type='text'>
There is an explicit wait-type violation in debug_object_fill_pool()
for PREEMPT_RT=n kernels which allows them to more easily fill the
object pool and reduce the chance of allocation failures.

Lockdep's wait-type checks are designed to check the PREEMPT_RT
locking rules even for PREEMPT_RT=n kernels and object to this, so
create a lockdep annotation to allow this to stand.

Specifically, create a 'lock' type that overrides the inner wait-type
while it is held -- allowing one to temporarily raise it, such that
the violation is hidden.

Reported-by: Vlastimil Babka &lt;vbabka@suse.cz&gt;
Reported-by: Qi Zheng &lt;zhengqi.arch@bytedance.com&gt;
Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Tested-by: Qi Zheng &lt;zhengqi.arch@bytedance.com&gt;
Link: https://lkml.kernel.org/r/20230429100614.GA1489784@hirez.programming.kicks-ass.net
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
There is an explicit wait-type violation in debug_object_fill_pool()
for PREEMPT_RT=n kernels which allows them to more easily fill the
object pool and reduce the chance of allocation failures.

Lockdep's wait-type checks are designed to check the PREEMPT_RT
locking rules even for PREEMPT_RT=n kernels and object to this, so
create a lockdep annotation to allow this to stand.

Specifically, create a 'lock' type that overrides the inner wait-type
while it is held -- allowing one to temporarily raise it, such that
the violation is hidden.

Reported-by: Vlastimil Babka &lt;vbabka@suse.cz&gt;
Reported-by: Qi Zheng &lt;zhengqi.arch@bytedance.com&gt;
Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Tested-by: Qi Zheng &lt;zhengqi.arch@bytedance.com&gt;
Link: https://lkml.kernel.org/r/20230429100614.GA1489784@hirez.programming.kicks-ass.net
</pre>
</div>
</content>
</entry>
<entry>
<title>locking/lockdep: Improve the deadlock scenario print for sync and read lock</title>
<updated>2023-03-27T18:16:04+00:00</updated>
<author>
<name>Boqun Feng</name>
<email>boqun.feng@gmail.com</email>
</author>
<published>2023-01-13T23:57:22+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=0471db447cb7de56bbe2fedd9256b4d2b8ef642a'/>
<id>0471db447cb7de56bbe2fedd9256b4d2b8ef642a</id>
<content type='text'>
Lock scenario print is always a weak spot of lockdep splats. Improvement
can be made if we rework the dependency search and the error printing.

However without touching the graph search, we can improve a little for
the circular deadlock case, since we have the to-be-added lock
dependency, and know whether these two locks are read/write/sync.

In order to know whether a held_lock is sync or not, a bit was
"stolen" from -&gt;references, which reduce our limit for the same lock
class nesting from 2^12 to 2^11, and it should still be good enough.

Besides, since we now have bit in held_lock for sync, we don't need the
"hardirqoffs being 1" trick, and also we can avoid the __lock_release()
if we jump out of __lock_acquire() before the held_lock stored.

With these changes, a deadlock case evolved with read lock and sync gets
a better print-out from:

	[...]  Possible unsafe locking scenario:
	[...]
	[...]        CPU0                    CPU1
	[...]        ----                    ----
	[...]   lock(srcuA);
	[...]                                lock(srcuB);
	[...]                                lock(srcuA);
	[...]   lock(srcuB);

to

	[...]  Possible unsafe locking scenario:
	[...]
	[...]        CPU0                    CPU1
	[...]        ----                    ----
	[...]   rlock(srcuA);
	[...]                                lock(srcuB);
	[...]                                lock(srcuA);
	[...]   sync(srcuB);

Signed-off-by: Boqun Feng &lt;boqun.feng@gmail.com&gt;
Signed-off-by: Paul E. McKenney &lt;paulmck@kernel.org&gt;
Acked-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Signed-off-by: Boqun Feng &lt;boqun.feng@gmail.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Lock scenario print is always a weak spot of lockdep splats. Improvement
can be made if we rework the dependency search and the error printing.

However without touching the graph search, we can improve a little for
the circular deadlock case, since we have the to-be-added lock
dependency, and know whether these two locks are read/write/sync.

In order to know whether a held_lock is sync or not, a bit was
"stolen" from -&gt;references, which reduce our limit for the same lock
class nesting from 2^12 to 2^11, and it should still be good enough.

Besides, since we now have bit in held_lock for sync, we don't need the
"hardirqoffs being 1" trick, and also we can avoid the __lock_release()
if we jump out of __lock_acquire() before the held_lock stored.

With these changes, a deadlock case evolved with read lock and sync gets
a better print-out from:

	[...]  Possible unsafe locking scenario:
	[...]
	[...]        CPU0                    CPU1
	[...]        ----                    ----
	[...]   lock(srcuA);
	[...]                                lock(srcuB);
	[...]                                lock(srcuA);
	[...]   lock(srcuB);

to

	[...]  Possible unsafe locking scenario:
	[...]
	[...]        CPU0                    CPU1
	[...]        ----                    ----
	[...]   rlock(srcuA);
	[...]                                lock(srcuB);
	[...]                                lock(srcuA);
	[...]   sync(srcuB);

Signed-off-by: Boqun Feng &lt;boqun.feng@gmail.com&gt;
Signed-off-by: Paul E. McKenney &lt;paulmck@kernel.org&gt;
Acked-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Signed-off-by: Boqun Feng &lt;boqun.feng@gmail.com&gt;
</pre>
</div>
</content>
</entry>
</feed>
