linux/kernel/pid.c, branch v2.6.19

[PATCH] introduce get_task_pid() to fix unsafe get_pid()

2006-10-02T14:57:25Z

proc_pid_make_inode: ei->pid = get_pid(task_pid(task)); I think this is not safe. get_pid() can be preempted after checking "pid != NULL". Then the task exits, does detach_pid(), and RCU frees the pid. Signed-off-by: Oleg Nesterov Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] Use struct pspace in next_pidmap and find_ge_pid

2006-10-02T14:57:15Z

This updates my proc: readdir race fix (take 3) patch to account for the changes made by: Sukadev Bhattiprolu to introduce struct pspace. Signed-off-by: Eric W. Biederman Cc: KAMEZAWA Hiroyuki Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] Define struct pspace

2006-10-02T14:57:15Z

Define a per-container pid space object. And create one instance of this object, init_pspace, to define the entire pid space. Subsequent patches will provide/use interfaces to create/destroy pid spaces. Its a subset/rework of Eric Biederman's patch http://lkml.org/lkml/2006/2/6/285 . Signed-off-by: Eric Biederman Signed-off-by: Sukadev Bhattiprolu Cc: Dave Hansen Cc: Serge Hallyn Cc: Cedric Le Goater Cc: Kirill Korotaev Cc: Andrey Savochkin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] Move pidmap to pspace.h

2006-10-02T14:57:15Z

Move struct pidmap and PIDMAP_ENTRIES to a new file, include/linux/pspace.h where it will be used in subsequent patches to define pid spaces. Its a subset of Eric Biederman's patch http://lkml.org/lkml/2006/2/6/285 [akpm@osdl.org: cleanups] Signed-off-by: Eric W. Biederman Signed-off-by: Sukadev Bhattiprolu Cc: Dave Hansen Cc: Serge Hallyn Cc: Cedric Le Goater Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] pids coding style use struct pidmap in next_pidmap

2006-10-02T14:57:15Z

Use struct pidmap instead of pidmap_t. This updates my proc: readdir race fix (take 3) patch to account for the changes made by: Sukadev Bhattiprolu to kill pidmap_t. Signed-off-by: Eric W. Biederman Cc: KAMEZAWA Hiroyuki Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] pids: coding style: use struct pidmap

2006-10-02T14:57:14Z

Use struct pidmap instead of pidmap_t. Its a subset of Eric Biederman's patch http://lkml.org/lkml/2006/2/6/271. Signed-off-by: Eric W. Biederman Signed-off-by: Sukadev Bhattiprolu Cc: Dave Hansen Cc: Serge Hallyn Cc: Cedric Le Goater Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] pid: export the symbols needed to use struct pid *

2006-10-02T14:57:13Z

pids aren't something that drivers should care about. However there are a lot of helper layers in the kernel that do care, and are built as modules. Before I can convert them to using struct pid instead of pid_t I need to export the appropriate symbols so they can continue to be built. Signed-off-by: Eric W. Biederman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] proc: readdir race fix (take 3)

2006-10-02T14:57:12Z

The problem: An opendir, readdir, closedir sequence can fail to report process ids that are continually in use throughout the sequence of system calls. For this race to trigger the process that proc_pid_readdir stops at must exit before readdir is called again. This can cause ps to fail to report processes, and it is in violation of posix guarantees and normal application expectations with respect to readdir. Currently there is no way to work around this problem in user space short of providing a gargantuan buffer to user space so the directory read all happens in on system call. This patch implements the normal directory semantics for proc, that guarantee that a directory entry that is neither created nor destroyed while reading the directory entry will be returned. For directory that are either created or destroyed during the readdir you may or may not see them. Furthermore you may seek to a directory offset you have previously seen. These are the guarantee that ext[23] provides and that posix requires, and more importantly that user space expects. Plus it is a simple semantic to implement reliable service. It is just a matter of calling readdir a second time if you are wondering if something new has show up. These better semantics are implemented by scanning through the pids in numerical order and by making the file offset a pid plus a fixed offset. The pid scan happens on the pid bitmap, which when you look at it is remarkably efficient for a brute force algorithm. Given that a typical cache line is 64 bytes and thus covers space for 64*8 == 200 pids. There are only 40 cache lines for the entire 32K pid space. A typical system will have 100 pids or more so this is actually fewer cache lines we have to look at to scan a linked list, and the worst case of having to scan the entire pid bitmap is pretty reasonable. If we need something more efficient we can go to a more efficient data structure for indexing the pids, but for now what we have should be sufficient. In addition this takes no additional locks and is actually less code than what we are doing now. Also another very subtle bug in this area has been fixed. It is possible to catch a task in the middle of de_thread where a thread is assuming the thread of it's thread group leader. This patch carefully handles that case so if we hit it we don't fail to return the pid, that is undergoing the de_thread dance. Thanks to KAMEZAWA Hiroyuki for providing the first fix, pointing this out and working on it. [oleg@tv-sign.ru: fix it] Signed-off-by: Eric W. Biederman Acked-by: KAMEZAWA Hiroyuki Signed-off-by: Oleg Nesterov Cc: Jean Delvare Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] pid: remove temporary debug code in attach_pid

2006-09-27T15:26:19Z

With the patches flying between Oleg and myself somehow this temporary debug code got left in pid.c. It was never intended to make it to the stable kernel. Signed-off-by: Eric W. Biederman Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] pid: Implement transfer_pid and use it to simplify de_thread

2006-09-27T15:26:19Z

In de_thread we move pids from one process to another, a rather ugly case. The function transfer_pid makes it clear what we are doing, and makes the action atomic. This is useful we ever want to atomically traverse the process group and session lists, in a rcu safe manner. Even if the atomic properties this change should be a win as transfer_pid should be less code to execute than executing both attach_pid and detach_pid, and this should make de_thread slightly smaller as only a single function call needs to be emitted. The only downside is that the code might be slower to execute as the odds are against transfer_pid being in cache. Signed-off-by: Eric W. Biederman Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds