<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux.git/mm/percpu.c, branch v5.4.301</title>
<subtitle>Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git</subtitle>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/'/>
<entry>
<title>treewide: Remove uninitialized_var() usage</title>
<updated>2023-06-09T08:29:01+00:00</updated>
<author>
<name>Kees Cook</name>
<email>keescook@chromium.org</email>
</author>
<published>2020-06-03T20:09:38+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=0638dcc7e75fbb766761e7b4694d0f0f141bbbd1'/>
<id>0638dcc7e75fbb766761e7b4694d0f0f141bbbd1</id>
<content type='text'>
commit 3f649ab728cda8038259d8f14492fe400fbab911 upstream.

Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings
(e.g. "unused variable"). If the compiler thinks it is uninitialized,
either simply initialize the variable or make compiler changes.

In preparation for removing[2] the[3] macro[4], remove all remaining
needless uses with the following script:

git grep '\buninitialized_var\b' | cut -d: -f1 | sort -u | \
	xargs perl -pi -e \
		's/\buninitialized_var\(([^\)]+)\)/\1/g;
		 s:\s*/\* (GCC be quiet|to make compiler happy) \*/$::g;'

drivers/video/fbdev/riva/riva_hw.c was manually tweaked to avoid
pathological white-space.

No outstanding warnings were found building allmodconfig with GCC 9.3.0
for x86_64, i386, arm64, arm, powerpc, powerpc64le, s390x, mips, sparc64,
alpha, and m68k.

[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Reviewed-by: Leon Romanovsky &lt;leonro@mellanox.com&gt; # drivers/infiniband and mlx4/mlx5
Acked-by: Jason Gunthorpe &lt;jgg@mellanox.com&gt; # IB
Acked-by: Kalle Valo &lt;kvalo@codeaurora.org&gt; # wireless drivers
Reviewed-by: Chao Yu &lt;yuchao0@huawei.com&gt; # erofs
Signed-off-by: Kees Cook &lt;keescook@chromium.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 3f649ab728cda8038259d8f14492fe400fbab911 upstream.

Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings
(e.g. "unused variable"). If the compiler thinks it is uninitialized,
either simply initialize the variable or make compiler changes.

In preparation for removing[2] the[3] macro[4], remove all remaining
needless uses with the following script:

git grep '\buninitialized_var\b' | cut -d: -f1 | sort -u | \
	xargs perl -pi -e \
		's/\buninitialized_var\(([^\)]+)\)/\1/g;
		 s:\s*/\* (GCC be quiet|to make compiler happy) \*/$::g;'

drivers/video/fbdev/riva/riva_hw.c was manually tweaked to avoid
pathological white-space.

No outstanding warnings were found building allmodconfig with GCC 9.3.0
for x86_64, i386, arm64, arm, powerpc, powerpc64le, s390x, mips, sparc64,
alpha, and m68k.

[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Reviewed-by: Leon Romanovsky &lt;leonro@mellanox.com&gt; # drivers/infiniband and mlx4/mlx5
Acked-by: Jason Gunthorpe &lt;jgg@mellanox.com&gt; # IB
Acked-by: Kalle Valo &lt;kvalo@codeaurora.org&gt; # wireless drivers
Reviewed-by: Chao Yu &lt;yuchao0@huawei.com&gt; # erofs
Signed-off-by: Kees Cook &lt;keescook@chromium.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>percpu: fix first chunk size calculation for populated bitmap</title>
<updated>2020-09-23T10:40:45+00:00</updated>
<author>
<name>Sunghyun Jin</name>
<email>mcsmonk@gmail.com</email>
</author>
<published>2020-09-03T12:41:16+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=e44bd84cd2ab06578bff58ea5e9af856ec63f47f'/>
<id>e44bd84cd2ab06578bff58ea5e9af856ec63f47f</id>
<content type='text'>
commit b3b33d3c43bbe0177d70653f4e889c78cc37f097 upstream.

Variable populated, which is a member of struct pcpu_chunk, is used as a
unit of size of unsigned long.
However, size of populated is miscounted. So, I fix this minor part.

Fixes: 8ab16c43ea79 ("percpu: change the number of pages marked in the first_chunk pop bitmap")
Cc: &lt;stable@vger.kernel.org&gt; # 4.14+
Signed-off-by: Sunghyun Jin &lt;mcsmonk@gmail.com&gt;
Signed-off-by: Dennis Zhou &lt;dennis@kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit b3b33d3c43bbe0177d70653f4e889c78cc37f097 upstream.

Variable populated, which is a member of struct pcpu_chunk, is used as a
unit of size of unsigned long.
However, size of populated is miscounted. So, I fix this minor part.

Fixes: 8ab16c43ea79 ("percpu: change the number of pages marked in the first_chunk pop bitmap")
Cc: &lt;stable@vger.kernel.org&gt; # 4.14+
Signed-off-by: Sunghyun Jin &lt;mcsmonk@gmail.com&gt;
Signed-off-by: Dennis Zhou &lt;dennis@kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>percpu: Use struct_size() helper</title>
<updated>2019-09-04T20:40:49+00:00</updated>
<author>
<name>Gustavo A. R. Silva</name>
<email>gustavo@embeddedor.com</email>
</author>
<published>2019-08-29T19:06:05+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=14d3761245551bdfc516abd8214a9f76bfd51435'/>
<id>14d3761245551bdfc516abd8214a9f76bfd51435</id>
<content type='text'>
One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct pcpu_alloc_info {
	...
        struct pcpu_group_info  groups[];
};

Make use of the struct_size() helper instead of an open-coded version
in order to avoid any potential type mistakes.

So, replace the following form:

sizeof(*ai) + nr_groups * sizeof(ai-&gt;groups[0])

with:

struct_size(ai, groups, nr_groups)

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva &lt;gustavo@embeddedor.com&gt;
Signed-off-by: Dennis Zhou &lt;dennis@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct pcpu_alloc_info {
	...
        struct pcpu_group_info  groups[];
};

Make use of the struct_size() helper instead of an open-coded version
in order to avoid any potential type mistakes.

So, replace the following form:

sizeof(*ai) + nr_groups * sizeof(ai-&gt;groups[0])

with:

struct_size(ai, groups, nr_groups)

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva &lt;gustavo@embeddedor.com&gt;
Signed-off-by: Dennis Zhou &lt;dennis@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>percpu: fix typo in pcpu_setup_first_chunk() comment</title>
<updated>2019-07-23T18:35:21+00:00</updated>
<author>
<name>Christophe JAILLET</name>
<email>christophe.jaillet@wanadoo.fr</email>
</author>
<published>2019-07-21T09:56:33+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=69ab285b682328ef7622f0567f8afebb00b404f3'/>
<id>69ab285b682328ef7622f0567f8afebb00b404f3</id>
<content type='text'>
s/perpcu/percpu/

Signed-off-by: Christophe JAILLET &lt;christophe.jaillet@wanadoo.fr&gt;
Signed-off-by: Dennis Zhou &lt;dennis@kernel.org&gt;
[Dennis: updated title]
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
s/perpcu/percpu/

Signed-off-by: Christophe JAILLET &lt;christophe.jaillet@wanadoo.fr&gt;
Signed-off-by: Dennis Zhou &lt;dennis@kernel.org&gt;
[Dennis: updated title]
</pre>
</div>
</content>
</entry>
<entry>
<title>percpu: Make pcpu_setup_first_chunk() void function</title>
<updated>2019-07-04T15:05:52+00:00</updated>
<author>
<name>Kefeng Wang</name>
<email>wangkefeng.wang@huawei.com</email>
</author>
<published>2019-07-03T08:25:52+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=163fa23435cc9c705a71001d4aa15f3f945554a1'/>
<id>163fa23435cc9c705a71001d4aa15f3f945554a1</id>
<content type='text'>
pcpu_setup_first_chunk() will panic or BUG_ON if the are some
error and doesn't return any error, hence it can be defined to
return void.

Reported-by: kbuild test robot &lt;lkp@intel.com&gt;
Signed-off-by: Kefeng Wang &lt;wangkefeng.wang@huawei.com&gt;
Signed-off-by: Dennis Zhou &lt;dennis@kernel.org&gt;
[Dennis: fixed kbuild warning for pcpu_page_first_chunk()]
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
pcpu_setup_first_chunk() will panic or BUG_ON if the are some
error and doesn't return any error, hence it can be defined to
return void.

Reported-by: kbuild test robot &lt;lkp@intel.com&gt;
Signed-off-by: Kefeng Wang &lt;wangkefeng.wang@huawei.com&gt;
Signed-off-by: Dennis Zhou &lt;dennis@kernel.org&gt;
[Dennis: fixed kbuild warning for pcpu_page_first_chunk()]
</pre>
</div>
</content>
</entry>
<entry>
<title>treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428</title>
<updated>2019-06-05T15:37:16+00:00</updated>
<author>
<name>Thomas Gleixner</name>
<email>tglx@linutronix.de</email>
</author>
<published>2019-06-01T08:08:42+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=55716d26439f5c4008b0bcb7f17d1f7c0d8fbcfc'/>
<id>55716d26439f5c4008b0bcb7f17d1f7c0d8fbcfc</id>
<content type='text'>
Based on 1 normalized pattern(s):

  this file is released under the gplv2

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 68 file(s).

Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Reviewed-by: Armijn Hemel &lt;armijn@tjaldur.nl&gt;
Reviewed-by: Allison Randal &lt;allison@lohutok.net&gt;
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190531190114.292346262@linutronix.de
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Based on 1 normalized pattern(s):

  this file is released under the gplv2

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 68 file(s).

Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Reviewed-by: Armijn Hemel &lt;armijn@tjaldur.nl&gt;
Reviewed-by: Allison Randal &lt;allison@lohutok.net&gt;
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190531190114.292346262@linutronix.de
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'for-5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu</title>
<updated>2019-05-13T22:34:03+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2019-05-13T22:34:03+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=3aff5fac54d722f363eac7db94536bffb55ca43f'/>
<id>3aff5fac54d722f363eac7db94536bffb55ca43f</id>
<content type='text'>
Pull percpu updates from Dennis Zhou:

 - scan hint update which helps address performance issues with heavily
   fragmented blocks

 - lockdep fix when freeing an allocation causes balance work to be
   scheduled

* 'for-5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu:
  percpu: remove spurious lock dependency between percpu and sched
  percpu: use chunk scan_hint to skip some scanning
  percpu: convert chunk hints to be based on pcpu_block_md
  percpu: make pcpu_block_md generic
  percpu: use block scan_hint to only scan forward
  percpu: remember largest area skipped during allocation
  percpu: add block level scan_hint
  percpu: set PCPU_BITMAP_BLOCK_SIZE to PAGE_SIZE
  percpu: relegate chunks unusable when failing small allocations
  percpu: manage chunks based on contig_bits instead of free_bytes
  percpu: introduce helper to determine if two regions overlap
  percpu: do not search past bitmap when allocating an area
  percpu: update free path with correct new free region
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull percpu updates from Dennis Zhou:

 - scan hint update which helps address performance issues with heavily
   fragmented blocks

 - lockdep fix when freeing an allocation causes balance work to be
   scheduled

* 'for-5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu:
  percpu: remove spurious lock dependency between percpu and sched
  percpu: use chunk scan_hint to skip some scanning
  percpu: convert chunk hints to be based on pcpu_block_md
  percpu: make pcpu_block_md generic
  percpu: use block scan_hint to only scan forward
  percpu: remember largest area skipped during allocation
  percpu: add block level scan_hint
  percpu: set PCPU_BITMAP_BLOCK_SIZE to PAGE_SIZE
  percpu: relegate chunks unusable when failing small allocations
  percpu: manage chunks based on contig_bits instead of free_bytes
  percpu: introduce helper to determine if two regions overlap
  percpu: do not search past bitmap when allocating an area
  percpu: update free path with correct new free region
</pre>
</div>
</content>
</entry>
<entry>
<title>percpu: remove spurious lock dependency between percpu and sched</title>
<updated>2019-05-08T19:08:48+00:00</updated>
<author>
<name>John Sperbeck</name>
<email>jsperbeck@google.com</email>
</author>
<published>2019-05-08T01:43:20+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=198790d9a3aeaef5792d33a560020861126edc22'/>
<id>198790d9a3aeaef5792d33a560020861126edc22</id>
<content type='text'>
In free_percpu() we sometimes call pcpu_schedule_balance_work() to
queue a work item (which does a wakeup) while holding pcpu_lock.
This creates an unnecessary lock dependency between pcpu_lock and
the scheduler's pi_lock.  There are other places where we call
pcpu_schedule_balance_work() without hold pcpu_lock, and this case
doesn't need to be different.

Moving the call outside the lock prevents the following lockdep splat
when running tools/testing/selftests/bpf/{test_maps,test_progs} in
sequence with lockdep enabled:

======================================================
WARNING: possible circular locking dependency detected
5.1.0-dbg-DEV #1 Not tainted
------------------------------------------------------
kworker/23:255/18872 is trying to acquire lock:
000000000bc79290 (&amp;(&amp;pool-&gt;lock)-&gt;rlock){-.-.}, at: __queue_work+0xb2/0x520

but task is already holding lock:
00000000e3e7a6aa (pcpu_lock){..-.}, at: free_percpu+0x36/0x260

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-&gt; #4 (pcpu_lock){..-.}:
       lock_acquire+0x9e/0x180
       _raw_spin_lock_irqsave+0x3a/0x50
       pcpu_alloc+0xfa/0x780
       __alloc_percpu_gfp+0x12/0x20
       alloc_htab_elem+0x184/0x2b0
       __htab_percpu_map_update_elem+0x252/0x290
       bpf_percpu_hash_update+0x7c/0x130
       __do_sys_bpf+0x1912/0x1be0
       __x64_sys_bpf+0x1a/0x20
       do_syscall_64+0x59/0x400
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-&gt; #3 (&amp;htab-&gt;buckets[i].lock){....}:
       lock_acquire+0x9e/0x180
       _raw_spin_lock_irqsave+0x3a/0x50
       htab_map_update_elem+0x1af/0x3a0

-&gt; #2 (&amp;rq-&gt;lock){-.-.}:
       lock_acquire+0x9e/0x180
       _raw_spin_lock+0x2f/0x40
       task_fork_fair+0x37/0x160
       sched_fork+0x211/0x310
       copy_process.part.43+0x7b1/0x2160
       _do_fork+0xda/0x6b0
       kernel_thread+0x29/0x30
       rest_init+0x22/0x260
       arch_call_rest_init+0xe/0x10
       start_kernel+0x4fd/0x520
       x86_64_start_reservations+0x24/0x26
       x86_64_start_kernel+0x6f/0x72
       secondary_startup_64+0xa4/0xb0

-&gt; #1 (&amp;p-&gt;pi_lock){-.-.}:
       lock_acquire+0x9e/0x180
       _raw_spin_lock_irqsave+0x3a/0x50
       try_to_wake_up+0x41/0x600
       wake_up_process+0x15/0x20
       create_worker+0x16b/0x1e0
       workqueue_init+0x279/0x2ee
       kernel_init_freeable+0xf7/0x288
       kernel_init+0xf/0x180
       ret_from_fork+0x24/0x30

-&gt; #0 (&amp;(&amp;pool-&gt;lock)-&gt;rlock){-.-.}:
       __lock_acquire+0x101f/0x12a0
       lock_acquire+0x9e/0x180
       _raw_spin_lock+0x2f/0x40
       __queue_work+0xb2/0x520
       queue_work_on+0x38/0x80
       free_percpu+0x221/0x260
       pcpu_freelist_destroy+0x11/0x20
       stack_map_free+0x2a/0x40
       bpf_map_free_deferred+0x3c/0x50
       process_one_work+0x1f7/0x580
       worker_thread+0x54/0x410
       kthread+0x10f/0x150
       ret_from_fork+0x24/0x30

other info that might help us debug this:

Chain exists of:
  &amp;(&amp;pool-&gt;lock)-&gt;rlock --&gt; &amp;htab-&gt;buckets[i].lock --&gt; pcpu_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(pcpu_lock);
                               lock(&amp;htab-&gt;buckets[i].lock);
                               lock(pcpu_lock);
  lock(&amp;(&amp;pool-&gt;lock)-&gt;rlock);

 *** DEADLOCK ***

3 locks held by kworker/23:255/18872:
 #0: 00000000b36a6e16 ((wq_completion)events){+.+.},
     at: process_one_work+0x17a/0x580
 #1: 00000000dfd966f0 ((work_completion)(&amp;map-&gt;work)){+.+.},
     at: process_one_work+0x17a/0x580
 #2: 00000000e3e7a6aa (pcpu_lock){..-.},
     at: free_percpu+0x36/0x260

stack backtrace:
CPU: 23 PID: 18872 Comm: kworker/23:255 Not tainted 5.1.0-dbg-DEV #1
Hardware name: ...
Workqueue: events bpf_map_free_deferred
Call Trace:
 dump_stack+0x67/0x95
 print_circular_bug.isra.38+0x1c6/0x220
 check_prev_add.constprop.50+0x9f6/0xd20
 __lock_acquire+0x101f/0x12a0
 lock_acquire+0x9e/0x180
 _raw_spin_lock+0x2f/0x40
 __queue_work+0xb2/0x520
 queue_work_on+0x38/0x80
 free_percpu+0x221/0x260
 pcpu_freelist_destroy+0x11/0x20
 stack_map_free+0x2a/0x40
 bpf_map_free_deferred+0x3c/0x50
 process_one_work+0x1f7/0x580
 worker_thread+0x54/0x410
 kthread+0x10f/0x150
 ret_from_fork+0x24/0x30

Signed-off-by: John Sperbeck &lt;jsperbeck@google.com&gt;
Signed-off-by: Dennis Zhou &lt;dennis@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
In free_percpu() we sometimes call pcpu_schedule_balance_work() to
queue a work item (which does a wakeup) while holding pcpu_lock.
This creates an unnecessary lock dependency between pcpu_lock and
the scheduler's pi_lock.  There are other places where we call
pcpu_schedule_balance_work() without hold pcpu_lock, and this case
doesn't need to be different.

Moving the call outside the lock prevents the following lockdep splat
when running tools/testing/selftests/bpf/{test_maps,test_progs} in
sequence with lockdep enabled:

======================================================
WARNING: possible circular locking dependency detected
5.1.0-dbg-DEV #1 Not tainted
------------------------------------------------------
kworker/23:255/18872 is trying to acquire lock:
000000000bc79290 (&amp;(&amp;pool-&gt;lock)-&gt;rlock){-.-.}, at: __queue_work+0xb2/0x520

but task is already holding lock:
00000000e3e7a6aa (pcpu_lock){..-.}, at: free_percpu+0x36/0x260

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-&gt; #4 (pcpu_lock){..-.}:
       lock_acquire+0x9e/0x180
       _raw_spin_lock_irqsave+0x3a/0x50
       pcpu_alloc+0xfa/0x780
       __alloc_percpu_gfp+0x12/0x20
       alloc_htab_elem+0x184/0x2b0
       __htab_percpu_map_update_elem+0x252/0x290
       bpf_percpu_hash_update+0x7c/0x130
       __do_sys_bpf+0x1912/0x1be0
       __x64_sys_bpf+0x1a/0x20
       do_syscall_64+0x59/0x400
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-&gt; #3 (&amp;htab-&gt;buckets[i].lock){....}:
       lock_acquire+0x9e/0x180
       _raw_spin_lock_irqsave+0x3a/0x50
       htab_map_update_elem+0x1af/0x3a0

-&gt; #2 (&amp;rq-&gt;lock){-.-.}:
       lock_acquire+0x9e/0x180
       _raw_spin_lock+0x2f/0x40
       task_fork_fair+0x37/0x160
       sched_fork+0x211/0x310
       copy_process.part.43+0x7b1/0x2160
       _do_fork+0xda/0x6b0
       kernel_thread+0x29/0x30
       rest_init+0x22/0x260
       arch_call_rest_init+0xe/0x10
       start_kernel+0x4fd/0x520
       x86_64_start_reservations+0x24/0x26
       x86_64_start_kernel+0x6f/0x72
       secondary_startup_64+0xa4/0xb0

-&gt; #1 (&amp;p-&gt;pi_lock){-.-.}:
       lock_acquire+0x9e/0x180
       _raw_spin_lock_irqsave+0x3a/0x50
       try_to_wake_up+0x41/0x600
       wake_up_process+0x15/0x20
       create_worker+0x16b/0x1e0
       workqueue_init+0x279/0x2ee
       kernel_init_freeable+0xf7/0x288
       kernel_init+0xf/0x180
       ret_from_fork+0x24/0x30

-&gt; #0 (&amp;(&amp;pool-&gt;lock)-&gt;rlock){-.-.}:
       __lock_acquire+0x101f/0x12a0
       lock_acquire+0x9e/0x180
       _raw_spin_lock+0x2f/0x40
       __queue_work+0xb2/0x520
       queue_work_on+0x38/0x80
       free_percpu+0x221/0x260
       pcpu_freelist_destroy+0x11/0x20
       stack_map_free+0x2a/0x40
       bpf_map_free_deferred+0x3c/0x50
       process_one_work+0x1f7/0x580
       worker_thread+0x54/0x410
       kthread+0x10f/0x150
       ret_from_fork+0x24/0x30

other info that might help us debug this:

Chain exists of:
  &amp;(&amp;pool-&gt;lock)-&gt;rlock --&gt; &amp;htab-&gt;buckets[i].lock --&gt; pcpu_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(pcpu_lock);
                               lock(&amp;htab-&gt;buckets[i].lock);
                               lock(pcpu_lock);
  lock(&amp;(&amp;pool-&gt;lock)-&gt;rlock);

 *** DEADLOCK ***

3 locks held by kworker/23:255/18872:
 #0: 00000000b36a6e16 ((wq_completion)events){+.+.},
     at: process_one_work+0x17a/0x580
 #1: 00000000dfd966f0 ((work_completion)(&amp;map-&gt;work)){+.+.},
     at: process_one_work+0x17a/0x580
 #2: 00000000e3e7a6aa (pcpu_lock){..-.},
     at: free_percpu+0x36/0x260

stack backtrace:
CPU: 23 PID: 18872 Comm: kworker/23:255 Not tainted 5.1.0-dbg-DEV #1
Hardware name: ...
Workqueue: events bpf_map_free_deferred
Call Trace:
 dump_stack+0x67/0x95
 print_circular_bug.isra.38+0x1c6/0x220
 check_prev_add.constprop.50+0x9f6/0xd20
 __lock_acquire+0x101f/0x12a0
 lock_acquire+0x9e/0x180
 _raw_spin_lock+0x2f/0x40
 __queue_work+0xb2/0x520
 queue_work_on+0x38/0x80
 free_percpu+0x221/0x260
 pcpu_freelist_destroy+0x11/0x20
 stack_map_free+0x2a/0x40
 bpf_map_free_deferred+0x3c/0x50
 process_one_work+0x1f7/0x580
 worker_thread+0x54/0x410
 kthread+0x10f/0x150
 ret_from_fork+0x24/0x30

Signed-off-by: John Sperbeck &lt;jsperbeck@google.com&gt;
Signed-off-by: Dennis Zhou &lt;dennis@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>percpu: stop printing kernel addresses</title>
<updated>2019-03-18T17:36:36+00:00</updated>
<author>
<name>Matteo Croce</name>
<email>mcroce@redhat.com</email>
</author>
<published>2019-03-18T01:32:36+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=00206a69ee32f03e6f40837684dcbe475ea02266'/>
<id>00206a69ee32f03e6f40837684dcbe475ea02266</id>
<content type='text'>
Since commit ad67b74d2469d9b8 ("printk: hash addresses printed with %p"),
at boot "____ptrval____" is printed instead of actual addresses:

    percpu: Embedded 38 pages/cpu @(____ptrval____) s124376 r0 d31272 u524288

Instead of changing the print to "%px", and leaking kernel addresses,
just remove the print completely, cfr. e.g. commit 071929dbdd865f77
("arm64: Stop printing the virtual memory layout").

Signed-off-by: Matteo Croce &lt;mcroce@redhat.com&gt;
Signed-off-by: Dennis Zhou &lt;dennis@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Since commit ad67b74d2469d9b8 ("printk: hash addresses printed with %p"),
at boot "____ptrval____" is printed instead of actual addresses:

    percpu: Embedded 38 pages/cpu @(____ptrval____) s124376 r0 d31272 u524288

Instead of changing the print to "%px", and leaking kernel addresses,
just remove the print completely, cfr. e.g. commit 071929dbdd865f77
("arm64: Stop printing the virtual memory layout").

Signed-off-by: Matteo Croce &lt;mcroce@redhat.com&gt;
Signed-off-by: Dennis Zhou &lt;dennis@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>percpu: use chunk scan_hint to skip some scanning</title>
<updated>2019-03-13T19:25:31+00:00</updated>
<author>
<name>Dennis Zhou</name>
<email>dennis@kernel.org</email>
</author>
<published>2019-02-26T18:46:48+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=d33d9f3dd96ba290bad3929f82990a0a7467ae90'/>
<id>d33d9f3dd96ba290bad3929f82990a0a7467ae90</id>
<content type='text'>
Just like blocks, chunks now maintain a scan_hint. This can be used to
skip some scanning by promoting the scan_hint to be the contig_hint.
The chunk's scan_hint is primarily updated on the backside and relies on
full scanning when a block becomes free or the free region spans across
blocks.

Signed-off-by: Dennis Zhou &lt;dennis@kernel.org&gt;
Reviewed-by: Peng Fan &lt;peng.fan@nxp.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Just like blocks, chunks now maintain a scan_hint. This can be used to
skip some scanning by promoting the scan_hint to be the contig_hint.
The chunk's scan_hint is primarily updated on the backside and relies on
full scanning when a block becomes free or the free region spans across
blocks.

Signed-off-by: Dennis Zhou &lt;dennis@kernel.org&gt;
Reviewed-by: Peng Fan &lt;peng.fan@nxp.com&gt;
</pre>
</div>
</content>
</entry>
</feed>
