/sys/kernel/debug/kmemleak empty despite kmemleak reports

[Paul Menzel]

Dear Catalin,


Am 09.07.20 um 19:57 schrieb Catalin Marinas:
> On Thu, Jul 09, 2020 at 04:37:10PM +0200, Paul Menzel wrote:
>> Despite Linux 5.8-rc4 reporting memory leaks on the IBM POWER 8 S822LC, the
>> file does not contain more information.
>>
>>> $ dmesg
>>> […] > [48662.953323] perf: interrupt took too long (2570 > 2500), lowering kernel.perf_event_max_sample_rate to 77750
>>> [48854.810636] perf: interrupt took too long (3216 > 3212), lowering kernel.perf_event_max_sample_rate to 62000
>>> [52300.044518] perf: interrupt took too long (4244 > 4020), lowering kernel.perf_event_max_sample_rate to 47000
>>> [52751.373083] perf: interrupt took too long (5373 > 5305), lowering kernel.perf_event_max_sample_rate to 37000
>>> [53354.000363] perf: interrupt took too long (6793 > 6716), lowering kernel.perf_event_max_sample_rate to 29250
>>> [53850.215606] perf: interrupt took too long (8672 > 8491), lowering kernel.perf_event_max_sample_rate to 23000
>>> [57542.266099] perf: interrupt took too long (10940 > 10840), lowering kernel.perf_event_max_sample_rate to 18250
>>> [57559.645404] perf: interrupt took too long (13714 > 13675), lowering kernel.perf_event_max_sample_rate to 14500
>>> [61608.697728] Can't find PMC that caused IRQ
>>> [71774.463111] kmemleak: 12 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
>>> [92372.044785] process '@/usr/bin/gnatmake-5' started with executable stack
>>> [92849.380672] FS-Cache: Loaded
>>> [92849.417269] FS-Cache: Netfs 'nfs' registered for caching
>>> [92849.595974] NFS: Registering the id_resolver key type
>>> [92849.596000] Key type id_resolver registered
>>> [92849.596000] Key type id_legacy registered
>>> [101808.079143] kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
>>> [106904.323471] Can't find PMC that caused IRQ
>>> [129416.391456] kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
>>> [158171.604221] kmemleak: 34 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
>>> $ sudo cat /sys/kernel/debug/kmemleak
> 
> When they are no longer present, they are most likely false positives.

How can this be? Shouldn’t the false positive also be logged in 
`/sys/kernel/debug/kmemleak`?

> Was this triggered during boot? Or under some workload?

 From the timestamps it looks like under some load.


Kind regards,

Paul