Re: cgroups commit 61d1d219c4 breaks systemd

[Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

(using Li's new address and quoting whole message for him)

The change has been in linux-next for quite some time and I've been
booting fedora 16 a lot of times on top of this.  Weird.  I'll try to
find out what's wrong and if I can't spot it quick enough, will send a
revert patch to Linus.  We can try again later.  Mandeep, any ideas?

Thanks.

On Thu, Mar 29, 2012 at 12:01:26AM +0200, Jiri Kosina wrote:
> Hi,
> 
> I am not able to boot current Linus' tree on system which is using 
> systemd. In the early boot phase I get
> 
> 	Failed to create root cgroup hierarchy: No such process
> 	Failed to allocate manager object: No such process
> 
> and that's it, the system is completely unusable afterwards (not having 
> any console spawned, no networking, etc).
> 
> Bisection pointed to
> 
> 	commit 61d1d219c4c0761059236a46867bc49943c4d29d
> 	Author: Mandeep Singh Baines <msb-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> 	Date:   Mon Jan 30 12:51:56 2012 -0800
> 
> 	    cgroup: remove extra calls to find_existing_css_set
> 
> and I have verified that reverting this single commit on top of current 
> Linus' tree makes the problem go away and the system boots properly.
> 
> strace output shows that with 61d1d219c applied, systemd is failing while 
> trying to add itself to the systemd cgroup:
> 
> mkdir("/sys", 0755)                     = -1 EEXIST (File exists)
> mkdir("/sys/fs", 0755)                  = -1 EEXIST (File exists)
> mkdir("/sys/fs/cgroup", 0755)           = -1 EEXIST (File exists)
> mkdir("/sys/fs/cgroup/systemd", 0755)   = -1 EEXIST (File exists)
> mkdir("/sys/fs/cgroup/systemd/system", 0755) = 0
> open("/sys/fs/cgroup/systemd/system/tasks", O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = 6
> fstat(6, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f60c4ecb000
> write(6, "357\n", 4)                    = -1 ESRCH (No such process)
> close(6)                                = 0
> munmap(0x7f60c4ecb000, 4096)            = 0
> writev(3, [{"<27>", 4}, {"systemd", 7}, {"[357]: ", 7}, {"Failed to create root cgroup hierarchy: No such process", 55}, {"\n", 1}], 5) = 74
> open("/sys/fs/cgroup/systemd/system/tasks", O_RDONLY|O_CLOEXEC) = 6
> fstat(6, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f60c4ecb000
> read(6, "357\n", 4096)                  = 4
> open("/sys/fs/cgroup/systemd/tasks", O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = 7
> fstat(7, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f60c4eca000
> write(7, "357\n", 4)                    = -1 ESRCH (No such process)
> close(7)                                = 0
> munmap(0x7f60c4eca000, 4096)            = 0
> read(6, "", 4096)                       = 0
> close(6)                                = 0
> munmap(0x7f60c4ecb000, 4096)            = 0
> open("/sys/fs/cgroup/systemd/system/tasks", O_RDONLY|O_CLOEXEC) = 6
> fstat(6, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f60c4ecb000
> read(6, "", 4096)                       = 0
> close(6)                                = 0
> munmap(0x7f60c4ecb000, 4096)            = 0
> open("/sys/fs/cgroup/systemd/system", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 6
> getdents(6, /* 7 entries */, 32768)     = 240
> getdents(6, /* 0 entries */, 32768)     = 0
> lstat("/sys/fs/cgroup/systemd/system/tasks", {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
> rmdir("/sys/fs/cgroup/systemd/system")  = 0
> close(6)                                = 0
> close(4)                                = 0
> close(5)                                = 0
> close(0)                                = 0
> writev(3, [{"<27>", 4}, {"systemd", 7}, {"[357]: ", 7}, {"Failed to allocate manager object: No such process", 50}, {"\n", 1}], 5) = 69

-- 
tejun