Messages in this thread | | | Date | Thu, 28 Apr 2005 10:21:34 +0100 | From | David Addison <> | Subject | Re: [PATCH][RFC] Linux VM hooks for advanced RDMA NICs |
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Brice Goglin wrote: >> @@ -267,6 +270,11 @@ >> >> unsigned long hiwater_rss; /* High-water RSS usage */ >> unsigned long hiwater_vm; /* High-water virtual memory usage */ >> + >> +#ifdef CONFIG_IOPROC >> + /* hooks for io devices with advanced RDMA capabilities */ >> + struct ioproc_ops *ioproc_ops; >> +#endif >> }; > >> +int >> +ioproc_register_ops(struct mm_struct *mm, struct ioproc_ops *ip) >> +{ >> + ip->next = mm->ioproc_ops; >> + mm->ioproc_ops = ip; >> + >> + return 0; >> +} >> + >> +EXPORT_SYMBOL_GPL(ioproc_register_ops); >> + >> +int >> +ioproc_unregister_ops(struct mm_struct *mm, struct ioproc_ops *ip) >> +{ >> + struct ioproc_ops **tmp; >> + >> + for (tmp = &mm->ioproc_ops; *tmp && *tmp != ip; tmp= &(*tmp)->next) >> + ; >> + if (*tmp) { >> + *tmp = ip->next; >> + return 0; >> + } >> + >> + return -EINVAL; >> +} >> + >> +EXPORT_SYMBOL_GPL(ioproc_unregister_ops); > > You don't seem to use any synchronization mechanism to protect the > ioproc list from concurrent modifications, right ? > I understand that it might be useless as long as QsNet is the only user > of ioprocs and takes care of locking the address space somewhere in the > driver before adding/removing hooks. > But, if this patch is to be merged to the mainline, you probably need > to do something here. It's not clear how other in-kernel users > (IB, Myri, Ammasso, ...) might use ioprocs. > And actually, I think all ioproc list traversal need to be protected > as well. > All ioproc list traversal is protected by the mm->page_table_lock which is held at all points where the callbacks are invoked. [Actually there is one case where this isn't true, which I'll fix when we refresh this patch later today]
The registration/unregister functions also need to be called holding this spinlock, our device driver does this, but perhaps we need to document that requirement more clearly.
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