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Date: Fri, 16 Oct 2009 09:45:17 +0200 From: Zdenek Kabelac <zdenek.kabelac@...il.com> To: Catalin Marinas <catalin.marinas@....com> Cc: Li Zefan <lizf@...fujitsu.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Steven Rostedt <rostedt@...dmis.org>, Frederic Weisbecker <fweisbec@...il.com>, Ingo Molnar <mingo@...e.hu> Subject: Re: Leaks in trace reported by kmemleak 2009/10/15 Catalin Marinas <catalin.marinas@....com>: > On Thu, 2009-10-15 at 17:46 +0800, Li Zefan wrote: >> Zdenek Kabelac wrote: >> > I've noticed your latest patch for memory leak in filter setting >> > (8ad807318fcd...) - but even with this patch - kmemleak seems to still >> > report lots (~900) of following leaks - note - they come only from >> > i915 and kvm module - so I'm not sure if these two modules are doing >> > something wrong or the problem is in trace code. >> > >> > It looks like whole directory is somehow forgotten. >> > >> >> Fortunately those are false-positives: >> >> # modprobe i915 >> # echo scan > /debug/kmemleak >> # cat /debug/kmemleak >> (lots of "leaks") >> # rmmod i915 >> # echo scan > /debug/kmemleak >> # cat /debug/kmemleak >> (no leaks) >> >> All the memory allocated when loading the module is >> freed in trace_module_remove_events() at module unload. >> >> But I haven't looked into how to suppress those false-postives. >> I'd like to, but I'm going to leave my office and won't be >> back until 26th.. > > It is probably caused by the fact that kmemleak doesn't scan the > mod->trace_events data in a module (the _ftrace_events section). It only > scans those sections beginning with .data and .bss in a module. Maybe we > should add "_ftrace_events" as well or just prefix it with ".data". > > Something like below may fix this (untested): > > diff --git a/kernel/module.c b/kernel/module.c > index 8b7d880..1449691 100644 > --- a/kernel/module.c > +++ b/kernel/module.c > @@ -2383,6 +2383,9 @@ static noinline struct module *load_module(void __user *umod, > "_ftrace_events", > sizeof(*mod->trace_events), > &mod->num_trace_events); > + kmemleak_scan_area(mod->module_core, mod->trace_events, > + sizeof(*mod->trace_events) * mod->num_trace_events, > + GFP_KERNEL); > #endif > #ifdef CONFIG_FTRACE_MCOUNT_RECORD > /* sechdrs[0].sh_size is always zero */ > > Yep - I've assume it could be also a problem of missing memory segment in kmemleak scanning routine - but it was weird that just these two modules (i915 & kvm) are doing such strange thing. I've tested patch above with added cast ( (unsigned long)mod->trace_events) to pacify warning - but it did not helped - leaks are still printed. And I add another leak - which might be from the same range of problem : (it's also present many times - and it even looks like hex dump is changing so it's probably even frequently used memory region - at least in few such objects) unreferenced object 0xffff88013aa4ad80 (size 192): comm "swapper", pid 1, jiffies 4294877809 hex dump (first 32 bytes): c0 dc a4 3a 01 88 ff ff 00 0c 79 39 01 88 ff ff ...:......y9.... 90 00 cf 3a 01 88 ff ff 02 00 00 00 00 00 00 00 ...:............ backtrace: [<ffffffff8140e9a6>] kmemleak_alloc+0x26/0x60 [<ffffffff81126a01>] kmem_cache_alloc_notrace+0xc1/0x140 [<ffffffff8127256a>] dma_debug_init+0x23a/0x3a0 [<ffffffff81864a37>] pci_iommu_init+0xe/0x28 [<ffffffff8100904c>] do_one_initcall+0x3c/0x1d0 [<ffffffff8185f4e6>] kernel_init+0x150/0x1a6 [<ffffffff8100d21a>] child_rip+0xa/0x20 [<ffffffffffffffff>] 0xffffffffffffffff Zdenek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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