Re: kmemleak: sched_domain_shared leaked on asymmetric-capacity + SCHED_CACHE

[Breno Leitao <leitao@debian.org>]

Hello Prateek,

On Fri, Jul 03, 2026 at 04:05:59PM +0530, K Prateek Nayak wrote:
> On 7/3/2026 3:52 PM, Breno Leitao wrote:
> > On current linux-next (CONFIG_SCHED_CACHE=y) we hit a kmemleak on an
> > arm64 box with asymmetric CPU capacity, triggered by a cpuset-driven
> > sched-domain rebuild:
> > 
> > kmemleak: unreferenced object 0xffff000100c95e80 (size 32):
> >   comm "kworker/22:1", pid 407, jiffies 4294669077
> >   hex dump (first 32 bytes):
> >     48 00 00 00 48 00 00 00 00 00 00 00 20 00 00 00  H...H....... ...
> >   backtrace (crc ec5d7053):
> >     __kmalloc_cache_node_noprof
> >     build_sched_domains
> >     partition_sched_domains
> >     rebuild_sched_domains_locked
> >     rebuild_sched_domains
> >     process_scheduled_works
> >     kthread
> >     ret_from_fork
> >   kmemleak: 1 new suspected memory leaks
> > 
> > The leaked object is a struct sched_domain_shared (32 bytes with
> > CONFIG_SCHED_CACHE) allocated in __sds_alloc(), inlined into
> > build_sched_domains()
> > 
> > Is this a known issue?
> 
> It is theoretically possible but there is a defensive WARN_ON()
> in topology code that you should have hit first. Do you see any
> other warning?
> 
> If it is not too much trouble, could you add "sched_verbose"
> to your kernel cmdline (or do
> echo Y > /sys/kernel/debug/sched/verbose) and redo this cpuset
> that leaks the data and share the dmesg. It should give some clue
> what the topology looks like that causes this.

Sure, does this one help:



  bash-5.1# cat /sys/kernel/debug/kmemleak
  unreferenced object 0xffff0000c1180820 (size 32):
    comm "swapper/0", pid 1, jiffies 4294667323
    hex dump (first 32 bytes):
      08 00 00 00 08 00 00 00 00 00 00 00 20 00 00 00  ............ ...
      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    backtrace (crc f4478cb7):
      kmemleak_alloc+0x44/0xd8
      __kmalloc_cache_node_noprof+0x344/0x5d8
      build_sched_domains+0x2f8/0x2110
      sched_init_domains+0xec/0x160
      sched_init_smp+0x48/0x108
      kernel_init_freeable+0x140/0x200
      kernel_init+0x30/0x170
      ret_from_fork+0x10/0x20
  
  bash-5.1# cd /sys/kernel/debug/sched/domains/
  
  bash-5.1# grep . -r *
  cpu0/domain0/level:1
  cpu0/domain0/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_ASYM_CPUCAPACITY SD_ASYM_CPUCAPACITY_FULL SD_SHARE_LLC SD_PREFER_SIBLING
  cpu0/domain0/name:MC
  cpu0/domain0/cache_nice_tries:1
  cpu0/domain0/imbalance_pct:117
  cpu0/domain0/busy_factor:16
  cpu0/domain0/max_newidle_lb_cost:2127
  cpu0/domain0/max_interval:16
  cpu0/domain0/min_interval:8
  cpu1/domain0/level:1
  cpu1/domain0/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_ASYM_CPUCAPACITY SD_ASYM_CPUCAPACITY_FULL SD_SHARE_LLC SD_PREFER_SIBLING
  cpu1/domain0/name:MC
  cpu1/domain0/cache_nice_tries:1
  cpu1/domain0/imbalance_pct:117
  cpu1/domain0/busy_factor:16
  cpu1/domain0/max_newidle_lb_cost:18112
  cpu1/domain0/max_interval:16
  cpu1/domain0/min_interval:8
  cpu2/domain0/level:1
  cpu2/domain0/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_ASYM_CPUCAPACITY SD_ASYM_CPUCAPACITY_FULL SD_SHARE_LLC SD_PREFER_SIBLING
  cpu2/domain0/name:MC
  cpu2/domain0/cache_nice_tries:1
  cpu2/domain0/imbalance_pct:117
  cpu2/domain0/busy_factor:16
  cpu2/domain0/max_newidle_lb_cost:3147
  cpu2/domain0/max_interval:16
  cpu2/domain0/min_interval:8
  cpu3/domain0/level:1
  cpu3/domain0/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_ASYM_CPUCAPACITY SD_ASYM_CPUCAPACITY_FULL SD_SHARE_LLC SD_PREFER_SIBLING
  cpu3/domain0/name:MC
  cpu3/domain0/cache_nice_tries:1
  cpu3/domain0/imbalance_pct:117
  cpu3/domain0/busy_factor:16
  cpu3/domain0/max_newidle_lb_cost:16399
  cpu3/domain0/max_interval:16
  cpu3/domain0/min_interval:8
  cpu4/domain0/level:1
  cpu4/domain0/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_ASYM_CPUCAPACITY SD_ASYM_CPUCAPACITY_FULL SD_SHARE_LLC SD_PREFER_SIBLING
  cpu4/domain0/name:MC
  cpu4/domain0/cache_nice_tries:1
  cpu4/domain0/imbalance_pct:117
  cpu4/domain0/busy_factor:16
  cpu4/domain0/max_newidle_lb_cost:27180
  cpu4/domain0/max_interval:16
  cpu4/domain0/min_interval:8
  cpu5/domain0/level:1
  cpu5/domain0/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_ASYM_CPUCAPACITY SD_ASYM_CPUCAPACITY_FULL SD_SHARE_LLC SD_PREFER_SIBLING
  cpu5/domain0/name:MC
  cpu5/domain0/cache_nice_tries:1
  cpu5/domain0/imbalance_pct:117
  cpu5/domain0/busy_factor:16
  cpu5/domain0/max_newidle_lb_cost:18384
  cpu5/domain0/max_interval:16
  cpu5/domain0/min_interval:8
  cpu6/domain0/level:1
  cpu6/domain0/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_ASYM_CPUCAPACITY SD_ASYM_CPUCAPACITY_FULL SD_SHARE_LLC SD_PREFER_SIBLING
  cpu6/domain0/name:MC
  cpu6/domain0/cache_nice_tries:1
  cpu6/domain0/imbalance_pct:117
  cpu6/domain0/busy_factor:16
  cpu6/domain0/max_newidle_lb_cost:16261
  cpu6/domain0/max_interval:16
  cpu6/domain0/min_interval:8
  cpu7/domain0/level:1
  cpu7/domain0/flags:SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_ASYM_CPUCAPACITY SD_ASYM_CPUCAPACITY_FULL SD_SHARE_LLC SD_PREFER_SIBLING
  cpu7/domain0/name:MC
  cpu7/domain0/cache_nice_tries:1
  cpu7/domain0/imbalance_pct:117
  cpu7/domain0/busy_factor:16
  cpu7/domain0/max_newidle_lb_cost:7780
  cpu7/domain0/max_interval:16
  cpu7/domain0/min_interval:8