lkml.org 
[lkml]   [2014]   [Jul]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: + shmem-fix-faulting-into-a-hole-while-its-punched-take-2.patch added to -mm tree
    On Thu, 10 Jul 2014, Sasha Levin wrote:
    > On 07/10/2014 02:52 PM, Hugh Dickins wrote:
    > > On Thu, 10 Jul 2014, Sasha Levin wrote:
    > >> > On 07/10/2014 01:55 PM, Hugh Dickins wrote:
    > >>>> > >> And finally, (not) holding the i_mmap_mutex:
    > >>> > > I don't understand what prompts you to show this particular task.
    > >>> > > I imagine the dump shows lots of other tasks which are waiting to get an
    > >>> > > i_mmap_mutex, and quite a lot of other tasks which are neither waiting
    > >>> > > for nor holding an i_mmap_mutex.
    > >>> > >
    > >>> > > Why are you showing this one in particular? Because it looks like the
    > >>> > > one you fingered yesterday? But I didn't see a good reason to finger
    > >>> > > that one either.
    > >> >
    > >> > There are a few more tasks like this one, my criteria was tasks that lockdep
    > >> > claims were holding i_mmap_mutex, but are actually not.
    > > You and Vlastimil enlightened me yesterday that lockdep shows tasks as
    > > holding i_mmap_mutex when they are actually waiting to get i_mmap_mutex.
    > > Hundreds of those in yesterday's log, hundreds of them in today's.
    >
    > What if we move lockdep's acquisition point to after it actually got the
    > lock?
    >
    > We'd miss deadlocks, but we don't care about them right now. Anyways, doesn't
    > lockdep have anything built in to allow us to separate between locks which
    > we attempt to acquire and locks that are actually acquired?
    >
    > (cc PeterZ)
    >
    > We can treat locks that are in the process of being acquired the same as
    > acquired locks to avoid races, but when we print something out it would
    > be nice to have annotation of the read state of the lock.

    I certainly hope someone can work on improving that. I imagine it would
    be easy, and well worth doing. But won't be looking into it myself.

    Hugh


    \
     
     \ /
      Last update: 2014-07-10 21:41    [W:3.323 / U:1.084 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site