Messages in this thread |  | | | Date | Sun, 23 Nov 2008 12:01:14 +0100 | | From | Ingo Molnar <> | | Subject | Re: [PATCH 2/3] tracing/stack-tracer: fix locking |
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* Török Edwin <edwintorok@gmail.com> wrote:
> On 2008-11-23 12:52, Ingo Molnar wrote: > > * Török Edwin <edwintorok@gmail.com> wrote: > > > > > >> + down_read(&mm->mmap_sem); > >> + vma = find_vma(mm, ip); > >> if (vma) { > >> file = vma->vm_file; > >> vmstart = vma->vm_start; > >> } > >> + up_read(&mm->mmap_sem); > >> } > >> if (file) { > >> ret = trace_seq_path(s, &file->f_path); > >> > > > > and now it's "file" that is held without a reference and possibly > > racy. > > > > I'll move the (file) inside the mmap_sem too, since file is part of > vma, and you need mmap_sem to access the vma nobody can modify > (file) if they don't hold mmap_sem. Am I right?
yeah - you can use the mm lock for that as the vma holds a reference to the file. This works as long as none of the seq functions called with this lock held can provoke a user pagefault (they shouldnt, but i havent checked in detail).
Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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