Messages in this thread | | | Subject | Re: [PATCH 1/2] kmemleak: Inform kmemleak about kernel stack allocation | From | Catalin Marinas <> | Date | Tue, 01 Sep 2009 10:25:14 +0100 |
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On Mon, 2009-08-31 at 10:45 +0200, Ingo Molnar wrote: > * Catalin Marinas <catalin.marinas@arm.com> wrote: > > > On Sat, 2009-08-29 at 15:29 +0200, Ingo Molnar wrote: > > > * Catalin Marinas <catalin.marinas@arm.com> wrote: [...] > > > > 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. > > I havent tried the patch myself, but by your description those build > problems seem to be pre-existing include file dependency problems > that should be tracked down and resolved - instead of widening them > by adding even more hidden dependencies via CPP macros.
I tried to move to an inline function and linux/gfp.h is needed for __get_free_pages() and GFP_* macros. This leads to some complicated circular dependencies like below:
CC arch/x86/kernel/asm-offsets.s In file included from /work/Linux/2.6/linux-2.6-arm/include/linux/mmzone.h:9, from /work/Linux/2.6/linux-2.6-arm/include/linux/gfp.h:4, from /work/Linux/2.6/linux-2.6-arm/arch/x86/include/asm/thread_info.h:22, from /work/Linux/2.6/linux-2.6-arm/include/linux/thread_info.h:56, from /work/Linux/2.6/linux-2.6-arm/include/linux/preempt.h:9, from /work/Linux/2.6/linux-2.6-arm/include/linux/spinlock.h:50, from /work/Linux/2.6/linux-2.6-arm/include/linux/seqlock.h:29, from /work/Linux/2.6/linux-2.6-arm/include/linux/time.h:8, from /work/Linux/2.6/linux-2.6-arm/include/linux/stat.h:60, from /work/Linux/2.6/linux-2.6-arm/include/linux/module.h:10, from /work/Linux/2.6/linux-2.6-arm/include/linux/crypto.h:21, from /work/Linux/2.6/linux-2.6-arm/arch/x86/kernel/asm-offsets_32.c:7, from /work/Linux/2.6/linux-2.6-arm/arch/x86/kernel/asm-offsets.c:2: include/linux/wait.h|51| error: expected specifier-qualifier-list before ‘spinlock_t’
The linux/mmzone.h file normally includes linux/spinlock.h but the reverse is also true when the latter includes the former via thread_info.h and gfp.h. Because of the (correct) guards in the header files, the spinlock_t definition is no longer available in mmzone.h.
Anyway, what I'd like with this patch is to reduce the latency caused by holding the tasklist_lock while scanning the stacks and also allow rescheduling. If you have 500 threads in a system with 8K stacks, kmemleak would need to scan about 4MB of stacks. While I think I can use rcu_read_lock/unlock around do_each_thread..while_each_thread, scheduling still isn't possible.
An alternative would be to traverse the tasks list for every stack scanned. This traversing should be negligible compared to a stack scanning time (looking up pointers in the prio tree).
Any opinion/suggestion here?
Thanks.
-- Catalin
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