I posted this on LKML a few weeks ago (http://lkml.org/lkml/2009/7/8/422) but I log it here as well so that it is not forgotten. I can consistently reproduce this leak on both x86 and ARM platforms as described in the original post, reproduced here: There's a kmemleak report of a struct pid allocation in alloc_pid() which somehow gets lost: unreferenced object 0xc307aa00 (size 44): comm "gdm", pid 2734, jiffies 4294902040 backtrace: [<c01e721a>] create_object+0xfa/0x250 [<c01e73cd>] kmemleak_alloc+0x5d/0x70 [<c01e0ad6>] kmem_cache_alloc+0x156/0x1a0 [<c01552f9>] alloc_pid+0x19/0x350 [<c013e6e0>] copy_process+0x800/0x1230 [<c013f17f>] do_fork+0x6f/0x370 [<c0101986>] sys_clone+0x36/0x40 [<c010319c>] sysenter_do_call+0x12/0x38 [<ffffffff>] 0xffffffff This is the gdm fork for starting Xorg (with pid 2739). It first logged me in automatically, after which I logged out and gdm started another Xorg. The pid structure for the first Xorg is reported as a leak. The Xorg with pid 2739 is no longer present on my system. Using gdb vmlinux /proc/kcore shows that the pid->count is 2, so that's why it probably wasn't freed by put_pid(): (gdb) print ({struct pid}0xc307aa00) $20 = {count = {counter = 2}, level = 0, tasks = {{first = 0x0}, { first = 0x0}, {first = 0x0}}, rcu = {next = 0xc24bfd64, func = 0xc0154e90 <delayed_put_pid>}, numbers = {{nr = 2739, ns = 0xc0737540, pid_chain = {next = 0x0, pprev = 0x200200}}}} Note that kmemleak is aware of and scans pid_hash (which was recorded in kmemleak as a 16KB object).
Created attachment 22531 [details] ARM .config file (RealView PB-A8 board)
Created attachment 22548 [details] x86 .config file
$ lsmod Module Size Used by tun 14532 0 i915 215720 2 drm 163168 3 i915 i2c_algo_bit 5920 1 i915 binfmt_misc 8484 1 ppdev 6920 0 lp 10020 0 parport 36296 2 ppdev,lp snd_hda_codec_realtek 201792 1 arc4 1820 2 snd_hda_intel 27048 3 snd_hda_codec 69172 2 snd_hda_codec_realtek,snd_hda_intel ecb 2748 2 snd_pcm_oss 39648 0 snd_mixer_oss 16996 1 snd_pcm_oss snd_pcm 76512 3 snd_hda_intel,snd_hda_codec,snd_pcm_oss joydev 10880 0 iwlagn 115684 0 iwlcore 113292 1 iwlagn snd_seq_dummy 2752 0 snd_seq_oss 28976 0 snd_seq_midi 6784 0 led_class 4272 1 iwlcore snd_rawmidi 22720 1 snd_seq_midi snd_seq_midi_event 7364 2 snd_seq_oss,snd_seq_midi snd_seq 51448 6 snd_seq_dummy,snd_seq_oss,snd_seq_midi,snd_seq_midi_event snd_timer 22144 2 snd_pcm,snd_seq mac80211 227992 2 iwlagn,iwlcore snd_seq_device 7408 5 snd_seq_dummy,snd_seq_oss,snd_seq_midi,snd_rawmidi,snd_seq pcspkr 2556 0 cfg80211 89572 3 iwlagn,iwlcore,mac80211 psmouse 56860 0 snd 61380 17 snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_seq_oss,snd_rawmidi,snd_seq,snd_timer,snd_seq_device serio_raw 5760 0 iTCO_wdt 11152 0 iTCO_vendor_support 3680 1 iTCO_wdt soundcore 7840 1 snd snd_page_alloc 9284 2 snd_hda_intel,snd_pcm video 18940 1 i915 output 3076 1 video intel_agp 27004 1 agpgart 36032 3 drm,intel_agp r8169 32960 0 mii 5276 1 r8169