https://github.com/torvalds/linux
Revision 696ac172fffa653dca401bb2b0cad91cf2ce453f authored by Johannes Weiner on 31 October 2013, 23:34:15 UTC, committed by Linus Torvalds on 31 October 2013, 23:58:13 UTC
When memcg code needs to know whether any given memcg has children, it uses the cgroup child iteration primitives and returns true/false depending on whether the iteration loop is executed at least once or not. Because a cgroup's list of children is RCU protected, these primitives require the RCU read-lock to be held, which is not the case for all memcg callers. This results in the following splat when e.g. enabling hierarchy mode: WARNING: CPU: 3 PID: 1 at kernel/cgroup.c:3043 css_next_child+0xa3/0x160() CPU: 3 PID: 1 Comm: systemd Not tainted 3.12.0-rc5-00117-g83f11a9-dirty #18 Hardware name: LENOVO 3680B56/3680B56, BIOS 6QET69WW (1.39 ) 04/26/2012 Call Trace: dump_stack+0x54/0x74 warn_slowpath_common+0x78/0xa0 warn_slowpath_null+0x1a/0x20 css_next_child+0xa3/0x160 mem_cgroup_hierarchy_write+0x5b/0xa0 cgroup_file_write+0x108/0x2a0 vfs_write+0xbd/0x1e0 SyS_write+0x4c/0xa0 system_call_fastpath+0x16/0x1b In the memcg case, we only care about children when we are attempting to modify inheritable attributes interactively. Racing with deletion could mean a spurious -EBUSY, no problem. Racing with addition is handled just fine as well through the memcg_create_mutex: if the child group is not on the list after the mutex is acquired, it won't be initialized from the parent's attributes until after the unlock. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 0056f4e
Tip revision: 696ac172fffa653dca401bb2b0cad91cf2ce453f authored by Johannes Weiner on 31 October 2013, 23:34:15 UTC
mm: memcg: fix test for child groups
mm: memcg: fix test for child groups
Tip revision: 696ac17
File | Mode | Size |
---|---|---|
Documentation | ||
arch | ||
block | ||
crypto | ||
drivers | ||
firmware | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.gitignore | -rw-r--r-- | 1.1 KB |
.mailmap | -rw-r--r-- | 4.4 KB |
COPYING | -rw-r--r-- | 18.3 KB |
CREDITS | -rw-r--r-- | 93.0 KB |
Kbuild | -rw-r--r-- | 2.5 KB |
Kconfig | -rw-r--r-- | 252 bytes |
MAINTAINERS | -rw-r--r-- | 259.6 KB |
Makefile | -rw-r--r-- | 47.4 KB |
README | -rw-r--r-- | 18.3 KB |
REPORTING-BUGS | -rw-r--r-- | 7.3 KB |
![swh spinner](/static/img/swh-spinner.gif)
Computing file changes ...