1. 20 Aug, 2008 1 commit
    • Peter Zijlstra's avatar
      printk: robustify printk, fix #2 · fa33507a
      Peter Zijlstra authored
      Dmitry Adamushko reported:
      
      > [*] btw., with DEBUG being enabled, pr_debug() generates [1] when
      > debug_smp_processor_id() is used (CONFIG_DEBUG_PREEMPT).
      >
      > the problem seems to be caused by the following commit:
      > commit b845b517
      > Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
      > Date:   Fri Aug 8 21:47:09 2008 +0200
      >
      >     printk: robustify printk
      >
      >
      > wake_up_klogd() -> __get_cpu_var() -> smp_processor_id()
      >
      > and that's being called from release_console_sem() which is, in turn,
      > said to be "may be called from any context" [2]
      >
      > and in this case, it seems to be called from some non-preemptible
      > context (although, it can't be printk()...
      > although, I haven't looked carefully yet).
      >
      > Provided [2], __get_cpu_var() is perhaps not the right solution there.
      >
      >
      > [1]
      >
      > [ 7697.942005] BUG: using smp_processor_id() in preemptible [00000000] code: syslogd/3542
      > [ 7697.942005] caller is wake_up_klogd+0x1b/0x50
      > [ 7697.942005] Pid: 3542, comm: syslogd Not tainted 2.6.27-rc3-tip-git #2
      > [ 7697.942005] Call Trace:
      > [ 7697.942005]  [<ffffffff8036b398>] debug_smp_processor_id+0xe8/0xf0
      > [ 7697.942005]  [<ffffffff80239d3b>] wake_up_klogd+0x1b/0x50
      > [ 7697.942005]  [<ffffffff8023a047>] release_console_sem+0x1e7/0x200
      > [ 7697.942005]  [<ffffffff803c0f17>] do_con_write+0xb7/0x1f30
      > [ 7697.942005]  [<ffffffff8020d920>] ? show_trace+0x10/0x20
      > [ 7697.942005]  [<ffffffff8020dc42>] ? dump_stack+0x72/0x80
      > [ 7697.942005]  [<ffffffff8036392d>] ? __ratelimit+0xbd/0xe0
      > [ 7697.942005]  [<ffffffff8036b398>] ? debug_smp_processor_id+0xe8/0xf0
      > [ 7697.942005]  [<ffffffff80239d3b>] ? wake_up_klogd+0x1b/0x50
      > [ 7697.942005]  [<ffffffff8023a047>] ? release_console_sem+0x1e7/0x200
      > [ 7697.942005]  [<ffffffff803c2de9>] con_write+0x19/0x30
      > [ 7697.942005]  [<ffffffff803b37b6>] write_chan+0x276/0x3c0
      > [ 7697.942005]  [<ffffffff80232b20>] ? default_wake_function+0x0/0x10
      > [ 7697.942005]  [<ffffffff804cb872>] ? _spin_lock_irqsave+0x22/0x50
      > [ 7697.942005]  [<ffffffff803b1334>] tty_write+0x194/0x260
      > [ 7697.942005]  [<ffffffff803b3540>] ? write_chan+0x0/0x3c0
      > [ 7697.942005]  [<ffffffff803b14a4>] redirected_tty_write+0xa4/0xb0
      > [ 7697.942005]  [<ffffffff803b1400>] ? redirected_tty_write+0x0/0xb0
      > [ 7697.942005]  [<ffffffff802a88c2>] do_loop_readv_writev+0x52/0x80
      > [ 7697.942005]  [<ffffffff802a939d>] do_readv_writev+0x1bd/0x1d0
      > [ 7697.942005]  [<ffffffff802a93e9>] vfs_writev+0x39/0x60
      > [ 7697.942005]  [<ffffffff802a9870>] sys_writev+0x50/0x90
      > [ 7697.942005]  [<ffffffff8020bb3b>] system_call_fastpath+0x16/0x1b
      Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Reported-by: default avatarDmitry Adamushko <dmitry.adamushko@gmail.com>
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      fa33507a
  2. 11 Aug, 2008 2 commits
  3. 08 Aug, 2008 37 commits