lkml.org 
[lkml]   [2011]   [Nov]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v7 3.2-rc2 3/30] uprobes: register/unregister probes.
    * Peter Zijlstra <peterz@infradead.org> [2011-11-28 16:29:54]:

    > On Fri, 2011-11-18 at 16:37 +0530, Srikar Dronamraju wrote:
    > > +static void __unregister_uprobe(struct inode *inode, loff_t offset,
    > > + struct uprobe *uprobe)
    > > +{
    > > + struct list_head try_list;
    > > + struct address_space *mapping;
    > > + struct vma_info *vi, *tmpvi;
    > > + struct vm_area_struct *vma;
    > > + struct mm_struct *mm;
    > > + loff_t vaddr;
    > > +
    > > + mapping = inode->i_mapping;
    > > + INIT_LIST_HEAD(&try_list);
    > > + while ((vi = find_next_vma_info(&try_list, offset,
    > > + mapping, false)) != NULL) {
    > > + if (IS_ERR(vi))
    > > + break;
    >
    > So what kind of half-assed state are we left in if we try an unregister
    > under memory pressure and how do we deal with that?
    >

    Agree, Even I had this concern and wanted to see if there are ways to
    deal with this.

    - One approach would be pass extra GFG flags while we do allocations
    atleast in the unregister_uprobe.

    Drawback of this approach: if the system is already under memory
    pressure we shouldnt exert more pressure by asking it to repeat.

    - The other approach would be to cache these temporary objects while we
    insert probes. i.e keep these metadata around.

    I am sure you wouldnt want to add additional metadata.

    - Third approach would be to have a completion/worker routine kick in if
    unregister_uprobe fails due to memory allocations.

    This looks better than the rest.

    Do you have any other approaches that we could try?

    --
    thanks and regards
    Srikar



    \
     
     \ /
      Last update: 2011-11-29 08:53    [W:0.042 / U:92.736 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site