kernel/linux.git/ipc/sem.c, branch v2.6.25.2

IPC: consolidate sem_exit_ns(), msg_exit_ns() and shm_exit_ns()

2008-02-08T17:22:26+00:00

sem_exit_ns(), msg_exit_ns() and shm_exit_ns() are all called when an ipc_namespace is released to free all ipcs of each type. But in fact, they do the same thing: they loop around all ipcs to free them individually by calling a specific routine. This patch proposes to consolidate this by introducing a common function, free_ipcs(), that do the job. The specific routine to call on each individual ipcs is passed as parameter. For this, these ipc-specific 'free' routines are reworked to take a generic 'struct ipc_perm' as parameter. Signed-off-by: Pierre Peiffer Cc: Cedric Le Goater Cc: Pavel Emelyanov Cc: Nadia Derbey Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

IPC: make struct ipc_ids static in ipc_namespace

2008-02-08T17:22:26+00:00

Each ipc_namespace contains a table of 3 pointers to struct ipc_ids (3 for msg, sem and shm, structure used to store all ipcs) These 'struct ipc_ids' are dynamically allocated for each icp_namespace as the ipc_namespace itself (for the init namespace, they are initialized with pointers to static variables instead) It is so for historical reason: in fact, before the use of idr to store the ipcs, the ipcs were stored in tables of variable length, depending of the maximum number of ipc allowed. Now, these 'struct ipc_ids' have a fixed size. As they are allocated in any cases for each new ipc_namespace, there is no gain of memory in having them allocated separately of the struct ipc_namespace. This patch proposes to make this table static in the struct ipc_namespace. Thus, we can allocate all in once and get rid of all the code needed to allocate and free these ipc_ids separately. Signed-off-by: Pierre Peiffer Acked-by: Cedric Le Goater Cc: Pavel Emelyanov Cc: Nadia Derbey Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

IPC/semaphores: consolidate SEM_STAT and IPC_STAT commands

2008-02-08T17:22:26+00:00

These commands (SEM_STAT and IPC_STAT) are rather doing the same things (only the meaning of the id given as input and the return value differ). However, for the semaphores, they are handled in two different places (two different functions). This patch consolidates this for clarification by handling these both commands in the same place in semctl_nolock(). It also removes one unused parameter for this function. Signed-off-by: Pierre Peiffer Cc: Nadia Derbey Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

namespaces: move the IPC namespace under IPC_NS option

2008-02-08T17:22:23+00:00

Currently the IPC namespace management code is spread over the ipc/*.c files. I moved this code into ipc/namespace.c file which is compiled out when needed. The linux/ipc_namespace.h file is used to store the prototypes of the functions in namespace.c and the stubs for NAMESPACES=n case. This is done so, because the stub for copy_ipc_namespace requires the knowledge of the CLONE_NEWIPC flag, which is in sched.h. But the linux/ipc.h file itself in included into many many .c files via the sys.h->sem.h sequence so adding the sched.h into it will make all these .c depend on sched.h which is not that good. On the other hand the knowledge about the namespaces stuff is required in 4 .c files only. Besides, this patch compiles out some auxiliary functions from ipc/sem.c, msg.c and shm.c files. It turned out that moving these functions into namespaces.c is not that easy because they use many other calls and macros from the original file. Moving them would make this patch complicated. On the other hand all these functions can be consolidated, so I will send a separate patch doing this a bit later. Signed-off-by: Pavel Emelyanov Acked-by: Serge Hallyn Cc: Cedric Le Goater Cc: "Eric W. Biederman" Cc: Herbert Poetzl Cc: Kirill Korotaev Cc: Sukadev Bhattiprolu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

IPC: fix error check in all new xxx_lock() and xxx_exit_ns() functions

2008-02-06T18:41:01+00:00

In the new implementation of the [sem|shm|msg]_lock[_check]() routines, we use the return value of ipc_lock() in container_of() without any check. But ipc_lock may return a errcode. The use of this errcode in container_of() may alter this errcode, and we don't want this. And in xxx_exit_ns, the pointer return by idr_find is of type 'struct kern_ipc_per'... Today, the code will work as is because the member used in these container_of() is the first member of its container (offset == 0), the errcode isn't changed then. But in the general case, we can't count on this assumption and this may lead later to a real bug if we don't correct this. Again, the proposed solution is simple and correct. But, as pointed by Nadia, with this solution, the same check will be done several times (in all sub-callers...), what is not very funny/optimal... Signed-off-by: Pierre Peiffer Cc: Nadia Derbey Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

IPC: fix error case when idr-cache is empty in ipcget()

2007-10-19T18:53:49+00:00

With the use of idr to store the ipc, the case where the idr cache is empty, when idr_get_new is called (this may happen even if we call idr_pre_get() before), is not well handled: it lets semget()/shmget()/msgget() return ENOSPC when this cache is empty, what 1. does not reflect the facts and 2. does not conform to the man(s). This patch fixes this by retrying the whole process of allocation in this case. Signed-off-by: Pierre Peiffer Cc: Nadia Derbey Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

IPC: cleanup some code and wrong comments about semundo list managment

2007-10-19T18:53:48+00:00

Some comments about sem_undo_list seem wrong. About the comment above unlock_semundo: "... If task2 now exits before task1 releases the lock (by calling unlock_semundo()), then task1 will never call spin_unlock(). ..." This is just wrong, I see no reason for which task1 will not call spin_unlock... The rest of this comment is also wrong... Unless I miss something (of course). Finally, (un)lock_semundo functions are useless, so remove them for simplification. (this avoids an useless if statement) Signed-off-by: Pierre Peiffer Cc: Nadia Derbey Acked-by: Serge Hallyn Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc: remove unneeded parameters

2007-10-19T18:53:48+00:00

Remvoe the unneeded parameters from ipc_checkid() and ipc_buildid() interfaces. Signed-off-by: Nadia Derbey Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

fix idr_find() locking

2007-10-19T18:53:48+00:00

This is a patch that fixes the way idr_find() used to be called in ipc_lock(): in all the paths that don't imply an update of the ipcs idr, it was called without the idr tree being locked. The changes are: . in ipc_ids, the mutex has been changed into a reader/writer semaphore. . ipc_lock() now takes the mutex as a reader during the idr_find(). . a new routine ipc_lock_down() has been defined: it doesn't take the mutex, assuming that it is being held by the caller. This is the routine that is now called in all the update paths. Signed-off-by: Nadia Derbey Acked-by: Jarek Poplawski Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc: fix wrong comments

2007-10-19T18:53:47+00:00

This patch fixes the wrong / obsolete comments in the ipc code. Also adds a missing lock around ipc_get_maxid() in shm_get_stat(). Signed-off-by: Nadia Derbey Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds