1. 07 Oct, 2010 1 commit
    • Jens Axboe's avatar
      elevator: fix oops on early call to elevator_change() · 430c62fb
      Jens Axboe authored
      2.6.36 introduces an API for drivers to switch the IO scheduler
      instead of manually calling the elevator exit and init functions.
      This API was added since q->elevator must be cleared in between
      those two calls. And since we already have this functionality
      directly from use by the sysfs interface to switch schedulers
      online, it was prudent to reuse it internally too.
      
      But this API needs the queue to be in a fully initialized state
      before it is called, or it will attempt to unregister elevator
      kobjects before they have been added. This results in an oops
      like this:
      
      BUG: unable to handle kernel NULL pointer dereference at 0000000000000051
      IP: [<ffffffff8116f15e>] sysfs_create_dir+0x2e/0xc0
      PGD 47ddfc067 PUD 47c6a1067 PMD 0
      Oops: 0000 [#1] PREEMPT SMP
      last sysfs file: /sys/devices/pci0000:00/0000:00:02.0/0000:04:00.1/irq
      CPU 2
      Modules linked in: t(+) loop hid_apple usbhid ahci ehci_hcd uhci_hcd libahci usbcore nls_base igb
      
      Pid: 7319, comm: modprobe Not tainted 2.6.36-rc6+ #132 QSSC-S4R/QSSC-S4R
      RIP: 0010:[<ffffffff8116f15e>]  [<ffffffff8116f15e>] sysfs_create_dir+0x2e/0xc0
      RSP: 0018:ffff88027da25d08  EFLAGS: 00010246
      RAX: ffff88047c68c528 RBX: 00000000fffffffe RCX: 0000000000000000
      RDX: 000000000000002f RSI: 000000000000002f RDI: ffff88047e196c88
      RBP: ffff88027da25d38 R08: 0000000000000000 R09: d84156c5635688c0
      R10: d84156c5635688c0 R11: 0000000000000000 R12: ffff88047e196c88
      R13: 0000000000000000 R14: 0000000000000000 R15: ffff88047c68c528
      FS:  00007fcb0b26f6e0(0000) GS:ffff880287400000(0000) knlGS:0000000000000000
      CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
      CR2: 0000000000000051 CR3: 000000047e76e000 CR4: 00000000000006e0
      DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
      DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
      Process modprobe (pid: 7319, threadinfo ffff88027da24000, task ffff88027d377090)
      Stack:
       ffff88027da25d58 ffff88047c68c528 00000000fffffffe ffff88047e196c88
      <0> ffff88047c68c528 ffff88047e05bd90 ffff88027da25d78 ffffffff8123fb77
      <0> ffff88047e05bd90 0000000000000000 ffff88047e196c88 ffff88047c68c528
      Call Trace:
       [<ffffffff8123fb77>] kobject_add_internal+0xe7/0x1f0
       [<ffffffff8123fd98>] kobject_add_varg+0x38/0x60
       [<ffffffff8123feb9>] kobject_add+0x69/0x90
       [<ffffffff8116efe0>] ? sysfs_remove_dir+0x20/0xa0
       [<ffffffff8103d48d>] ? sub_preempt_count+0x9d/0xe0
       [<ffffffff8143de20>] ? _raw_spin_unlock+0x30/0x50
       [<ffffffff8116efe0>] ? sysfs_remove_dir+0x20/0xa0
       [<ffffffff8116eff4>] ? sysfs_remove_dir+0x34/0xa0
       [<ffffffff81224204>] elv_register_queue+0x34/0xa0
       [<ffffffff81224aad>] elevator_change+0xfd/0x250
       [<ffffffffa007e000>] ? t_init+0x0/0x361 [t]
       [<ffffffffa007e000>] ? t_init+0x0/0x361 [t]
       [<ffffffffa007e0a8>] t_init+0xa8/0x361 [t]
       [<ffffffff810001de>] do_one_initcall+0x3e/0x170
       [<ffffffff8108c3fd>] sys_init_module+0xbd/0x220
       [<ffffffff81002f2b>] system_call_fastpath+0x16/0x1b
      Code: e5 41 56 41 55 41 54 49 89 fc 53 48 83 ec 10 48 85 ff 74 52 48 8b 47 18 49 c7 c5 00 46 61 81 48 85 c0 74 04 4c 8b 68 30 45 31 f6 <41> 80 7d 51 00 74 0e 49 8b 44 24 28 4c 89 e7 ff 50 20 49 89 c6
      RIP  [<ffffffff8116f15e>] sysfs_create_dir+0x2e/0xc0
       RSP <ffff88027da25d08>
      CR2: 0000000000000051
      ---[ end trace a6541d3bf07945df ]---
      
      Fix this by adding a registered bit to the elevator queue, which is
      set when the sysfs kobjects have been registered.
      Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
      430c62fb
  2. 06 Oct, 2010 6 commits
  3. 05 Oct, 2010 6 commits
  4. 04 Oct, 2010 27 commits