Messages in this thread | | | Date | Mon, 15 Apr 2013 18:27:42 -0700 (PDT) | From | Hugh Dickins <> | Subject | Re: 3.9-rc5: Encountedred INFO: rcu_sched self-detected stall on CPU due to 09a9f1d27 |
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On Mon, 15 Apr 2013, Michel Lespinasse wrote: > On Mon, Apr 15, 2013 at 2:47 PM, Hugh Dickins <hughd@google.com> wrote: > > --- 3.9-rc7/mm/mlock.c 2013-04-01 09:08:05.736012852 -0700 > > +++ linux/mm/mlock.c 2013-04-15 14:20:24.454773245 -0700 > > @@ -397,8 +397,7 @@ int __mm_populate(unsigned long start, u > > long ret = 0; > > > > VM_BUG_ON(start & ~PAGE_MASK); > > - VM_BUG_ON(len != PAGE_ALIGN(len)); > > - end = start + len; > > + end = start + PAGE_ALIGN(len); > > > > for (nstart = start; nstart < end; nstart = nend) { > > /* > > Yes, there was originally an issue with page alignment in mmap as well, which was fixed by making sure mmap now passes the page aligned length to mm_populate(). > > sys_brk() passes the length as the difference of two page aligned addresses, so it's fine. But vm_brk() doesn't - it calls do_brk() which page aligns the length, but then vm_brk passes the unaligned length to mm_populate(). > > What do you think of the following ? len is already a PAGE_SIZE multiple when called from sys_brk()...
Yes, that's good.
> > diff --git a/mm/mmap.c b/mm/mmap.c > index 0db0de1c2fbe..6af8b0d1c7db 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -2557,10 +2557,6 @@ static unsigned long do_brk(unsigned long addr, unsigned long len) > pgoff_t pgoff = addr >> PAGE_SHIFT; > int error; > > - len = PAGE_ALIGN(len); > - if (!len) > - return addr; > - > flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags; > > error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED); > @@ -2643,6 +2639,10 @@ unsigned long vm_brk(unsigned long addr, unsigned long len) > unsigned long ret; > bool populate; > > + len = PAGE_ALIGN(len); > + if (!len) > + return addr; > + > down_write(&mm->mmap_sem); > ret = do_brk(addr, len); > populate = ((mm->def_flags & VM_LOCKED) != 0); > > -- > Michel "Walken" Lespinasse > A program is never fully debugged until the last user dies.
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