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    SubjectRe: [PATCH 1/2] kmemleak: Inform kmemleak about kernel stack allocation
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    On Sat, 2009-08-29 at 15:28 +0100, Catalin Marinas wrote:
    > On Sat, 2009-08-29 at 15:29 +0200, Ingo Molnar wrote:
    > > * Catalin Marinas <catalin.marinas@arm.com> wrote:
    > >
    > > > Traversing all the tasks in the system for scanning the kernel
    > > > stacks requires locking which increases the kernel latency
    > > > considerably. This patch informs kmemleak about newly allocated or
    > > > freed stacks so that they are treated as any other allocated
    > > > object. Subsequent patch will remove the explicit stack scanning
    > > > from mm/kmemleak.c.
    > > >
    > > > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
    > > > Cc: Ingo Molnar <mingo@redhat.com>
    > > > ---
    > > > arch/x86/include/asm/thread_info.h | 7 ++++++-
    > > > arch/x86/kernel/process.c | 2 ++
    > > > kernel/fork.c | 7 ++++++-
    > > > 3 files changed, 14 insertions(+), 2 deletions(-)
    > > >
    > > > diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
    > > > index fad7d40..f26432a 100644
    > > > --- a/arch/x86/include/asm/thread_info.h
    > > > +++ b/arch/x86/include/asm/thread_info.h
    > > > @@ -162,7 +162,12 @@ struct thread_info {
    > > > #define __HAVE_ARCH_THREAD_INFO_ALLOCATOR
    > > >
    > > > #define alloc_thread_info(tsk) \
    > > > - ((struct thread_info *)__get_free_pages(THREAD_FLAGS, THREAD_ORDER))
    > > > +({ \
    > > > + struct thread_info *ti = (struct thread_info *) \
    > > > + __get_free_pages(THREAD_FLAGS, THREAD_ORDER); \
    > > > + kmemleak_alloc(ti, THREAD_SIZE, 1, THREAD_FLAGS); \
    > > > + ti; \
    > > > +})
    > >
    > > Sidenote:this used to be a trivial wrapper to gfp so it was
    > > borderline OK as a CPP macro - now it's a non-trivial CPP wrapper
    > > macro which is not OK. Mind converting it to an inline function?
    >
    > I tried this first but got compilation errors in files that didn't even
    > call this function. To make it workable, thread_info.h would need to
    > include additional headers. If that's acceptable, I can post an updated
    > patch.

    Actually I think it's only the kmemleak.h header but it would get
    included via thread_info.h in many other files. An alternative is to
    make kmemleak_alloc() etc. return the pointer passed as argument and
    keep the macro something like:

    kmemleak_alloc(__get_free_pages(...), ...)

    though it is still a bit long.

    --
    Catalin



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