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Two false positives from debugging tools (lockdep, kmemleak)

Jonathan Nieder lkml 1 version New

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  1. v1 Latest2 patches 0 repliesNew

Patches in v1 No applies recorded yet

#Subject and filesSizeRepliesApplied
1/2cgroup/kmemleak: Annotate alloc_page() for cgroup allocationsmm/page_cgroup.c+5 -20 replies
2/2epoll: fix spurious lockdep warningsfs/eventpoll.c+18 -70 replies

Reviews trailers per patch

All 2 patches have a Reviewed-by or Acked-by.

PatchMichal HockoCatalin MarinasPaul BolleJason Baron
1/2R-b A-b
2/2T-b A-b

Trailers given in replies are filled; those carried in the patches from earlier versions are outlined with dashes. Scroll the table sideways for all 4 reviewers.

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Cover letter [PATCH 3.1-rc8 0/2] Two false positives from debugging tools (lockdep, kmemleak)

Hi,

Especially during the -rc period, it is nice to be able to take advantage of lockdep and kmemleak to find bugs. False positives make it harder to find real problems amid the noise.

At boot time, I get:

| allocated 14680064 bytes of page_cgroup
| please try 'cgroup_disable=memory' option if you don't want memory cgroups
| kmemleak: Trying to color unknown object at 0xffff88006f500000 as Grey
| Pid: 0, comm: swapper Not tainted 3.1.0-rc8-00031-gd5767c53535a #12
| Call Trace:
|  [<ffffffff810f8637>] paint_ptr+0x56/0x8e
|  [<ffffffff812e336c>] kmemleak_not_leak+0x23/0x42
|  [<ffffffff816a00d5>] kmemleak_init+0x1db/0x23a
|  [<ffffffff81686ad2>] start_kernel+0x31c/0x3b1
|  [<ffffffff816862a8>] x86_64_start_reservations+0xaf/0xb3
|  [<ffffffff81686140>] ? early_idt_handlers+0x140/0x140
|  [<ffffffff816863ae>] x86_64_start_kernel+0x102/0x111
| kmemleak: Trying to color unknown object at 0xffff88006f600000 as Grey

[and so on, for 13 addresses in all]

Also:

| [  222.425445] systemd-logind/908 is trying to acquire lock:
| [  222.425447]  (&ep->mtx){+.+.+.}, at: [<ffffffff8112da68>] ep_scan_ready_list+0x3c/0x1a7
| [  222.425456] 
| [  222.425457] but task is already holding lock:
| [  222.425459]  (&ep->mtx){+.+.+.}, at: [<ffffffff8112dfd8>] sys_epoll_ctl+0x11d/0x520

Luckily both false positives seem to be known and well understood. The first of the patches below (the kmemleak one) seems to have fallen under the radar --- I can't even find it in linux-next. The second (the lockdep one) is taken from akpm's -mm patchset.

Thoughts?

Nelson Elhage (1):
epoll: fix spurious lockdep warnings

Steven Rostedt (1):
cgroup/kmemleak: Annotate alloc_page() for cgroup allocations

 fs/eventpoll.c   |   25 ++++++++++++++++++-------
 mm/page_cgroup.c |    7 +++++--
 2 files changed, 23 insertions(+), 9 deletions(-)
Signature · 1 line
1.7.7.rc1