lkml.org 
[lkml]   [2007]   [Oct]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: BUG: lock held when returning to user space
    From
    Date

    On Sat, 2007-10-27 at 17:12 +0200, Jiri Kosina wrote:
    > On Sat, 27 Oct 2007, Gabriel C wrote:
    >
    > > I found that today in dmesg after booting current git (
    > > ec3b67c11df42362ccda81261d62829042f223f0 ) :
    > > ...
    > > [ 592.752777]
    > > [ 592.752781] ================================================
    > > [ 592.753478] [ BUG: lock held when returning to user space! ]
    > > [ 592.753880] ------------------------------------------------
    > > [ 592.754262] hwclock/1452 is leaving the kernel with locks still held!
    > > [ 592.754655] 1 lock held by hwclock/1452:
    > > [ 592.755007] #0: (&rtc->char_lock){--..}, at: [<c02a7ebb>] rtc_dev_open+0x2e/0x7e
    >
    > Yes, this is because rtc keeps a char_lock mutex locked as long as the
    > device is open, to avoid concurrent accessess.
    >
    > It could be easily substituted by some counting -- setting and clearing
    > bit in struct rtc_device instead of using char_lock, but doing this just
    > to shut the lockdep off is questionable imho.
    >
    > Peter, what is the preferred way to annotate these kinds of locking for
    > lockdep to express that it is intended?

    Not sure, I'd not thought that anyone would actually want to do this.
    I'm also not sure how I stand on this, I'd prefer to say: don't do this!

    I think, in this case, the lock is associated with a kernel object that
    is properly cleaned up if the holding tasks gets a SIGKILL. But in
    general I'd like to see this kind of thing go away.

    Now I could probably come up with an annotation to hide it, but what do
    other people think, Ingo, Linus, Andrew, do we want to keep kernel locks
    held over userspace?



    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-10-27 17:33    [W:0.022 / U:0.804 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site