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[Brad Figg <brad.figg@xxxxxxxxxxxxx>]

This bug is missing log files that will aid in diagnosing the problem.
>From a terminal window please run:

apport-collect 1341364

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable
to run this command, please add a comment stating that fact and change
the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the
Ubuntu Kernel Team.

** Changed in: linux (Ubuntu)
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1341364

Title:
  cgroupfs rmdir race (regression)

Status in “linux” package in Ubuntu:
  Incomplete

Bug description:
  In older utopic kernels (abi-3.15.0-6-generic), when I quickly rmdir
  /a/b and then rmdir /a, it succeeds.  With the kernel in utopic, the
  rmdir of cgroup /a fails with EBUSY.  This appears to be a race.

  The following test program quite reliably shows the race:

  #include <stdio.h>                                         
  #include <stdlib.h>                                           
  #include <sys/stat.h>
  #include <sys/types.h>
  #include <sys/mount.h>
  #include <errno.h>
  #include <string.h>
   
  int main()
  {
          int ret;
          int i;
          char path[1024], f[30];

          ret = mount("cgroup", "/mnt", "cgroup", 0, "memory");
          if (ret) {
                  perror("mount");
                  exit(1);
          }
                
          sprintf(path, "/mnt");
          printf("creating\n");
          for (i = 0; i < 10; i++) {
                  sprintf(f, "/dir%d", i);
                  strcat(path, f);
                  ret = mkdir(path, 0755);
                  if (ret && errno != EEXIST) {
                          perror("mkdir");
                          printf("Failed on %d\n", i);
                          umount("/mnt");
                          exit(1);
                  }
          }                                      
          printf("Now removing\n");                      
          for (i = 9;  i >= 0;  i--) {                                        
                  ret = rmdir(path);
                  if (ret) {                               
                          perror("rmdir");                         
                          printf("Failed removing %s\n", path);
                          umount("/mnt");
                          exit(1);
                  }
                  char *p = strrchr(path, '/');
                  *p = '\0';
          }                            
          umount("/mnt");                      
          printf("Done - success\n");
  }                                  

  This is also blocking promotion of the cgmanager package to utopic due
  to jenkins failure:

  
  https://jenkins.qa.ubuntu.com/job/utopic-adt-cgmanager/30/ARCH=amd64,label=adt/console

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