> > There's more cases, I forgot the details of how the prio_tree stuff > works, so please consider if its possible to also have: > > __unregister_uprobe() will observe neither old nor new > > This could happen if we first munmap, __unregister_uprobe() will iterate > past where mmap() will insert the new vma, mmap will insert the new vma, > and __unregister_uprobe() will now not observe it. > - When we iterate thro __unregister_uprobe(), we always walk from the root of the prio tree and not depend on the last found node. So __unregister_uprobe able to iterate thro the rmap without finding the old or the new vma would mean that the exclusive mmap_sem was dropped for atleast a brief period and munmap/mmap are disjoint. Here munmap_uprobe would have reduced the count followed by the pages being cleared. __unregister_uprobe maintains the status quo. mmap_uprobe would load a new set of pages without any breakpoint, since there are no consumers, and no underlying breakpoints, it also maintains the status quo. > and > > __unregister_uprobe() will observe both old _and_ new > > This latter could happen by favourably interleaving the prio_tree > iteration with the munmap and mmap operations, so that we first observe > the old vma, do the munmap, do the mmap, and then have the > find_next_vma_info() thing find the new vma. If __unregister_uprobe() can observe both old _and_ new, then it means mmap has occurred. So its correct that probes are removed from the old and new. The munmap_uprobe of the old vma wouldnt see the breakpoint (via read_opcode) so wont decrement the count. If the munmap_uprobe had seen the breakpoint before unregister_uprobe, then unregister_uprobe cant decrement the count. -- Thanks and Regards Srikar -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>