20 Oct, 2007
15 commits
-
Since these are expanded into call to pid_nr_ns() anyway, it's OK to move
the whole routine out-of-line. This is a cheap way to save ~100 bytes from
vmlinux. Together with the previous two patches, it saves half-a-kilo from
the vmlinux.Un-inline other (currently inlined) functions must be done with additional
performance testing.Signed-off-by: Pavel Emelyanov
Cc: Sukadev Bhattiprolu
Cc: Oleg Nesterov
Cc: Paul Menage
Cc: "Eric W. Biederman"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The find_pid/_vpid/_pid_ns functions are used to find the struct pid by its
id, depending on whic id - global or virtual - is used.The find_vpid() is a macro that pushes the current->nsproxy->pid_ns on the
stack to call another function - find_pid_ns(). It turned out, that this
dereference together with the push itself cause the kernel text size to
grow too much.Move all these out-of-line. Together with the previous patch this saves a
bit less that 400 bytes from .text section.Signed-off-by: Pavel Emelyanov
Cc: Sukadev Bhattiprolu
Cc: Oleg Nesterov
Cc: Paul Menage
Cc: "Eric W. Biederman"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Since we've switched from using pid->nr to pid->upids->nr some
fields on struct pid are no longer neededSigned-off-by: Pavel Emelyanov
Cc: Oleg Nesterov
Cc: Sukadev Bhattiprolu
Cc: Paul Menage
Cc: "Eric W. Biederman"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The find_task_by_something is a set of macros are used to find task by pid
depending on what kind of pid is proposed - global or virtual one. All of
them are wrappers above the most generic one - find_task_by_pid_type_ns() -
and just substitute some args for it.It turned out, that dereferencing the current->nsproxy->pid_ns construction
and pushing one more argument on the stack inline cause kernel text size to
grow.This patch moves all this stuff out-of-line into kernel/pid.c. Together
with the next patch it saves a bit less than 400 bytes from the .text
section.Signed-off-by: Pavel Emelyanov
Cc: Sukadev Bhattiprolu
Cc: Oleg Nesterov
Cc: Paul Menage
Cc: "Eric W. Biederman"
Acked-by: Ingo Molnar
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Terminate all processes in a namespace when the reaper of the namespace is
exiting. We do this by walking the pidmap of the namespace and sending
SIGKILL to all processes.Signed-off-by: Sukadev Bhattiprolu
Acked-by: Pavel Emelyanov
Cc: Oleg Nesterov
Cc: Sukadev Bhattiprolu
Cc: Paul Menage
Cc: "Eric W. Biederman"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This will help fixing memory leaks due to bad reference counting.
Signed-off-by: Sukadev Bhattiprolu
Cc: Oleg Nesterov
Cc: Sukadev Bhattiprolu
Cc: Paul Menage
Cc: "Eric W. Biederman"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
When clone() is invoked with CLONE_NEWPID, create a new pid namespace and then
create a new struct pid for the new process. Allocate pid_t's for the new
process in the new pid namespace and all ancestor pid namespaces. Make the
newly cloned process the session and process group leader.Since the active pid namespace is special and expected to be the first entry
in pid->upid_list, preserve the order of pid namespaces.The size of 'struct pid' is dependent on the the number of pid namespaces the
process exists in, so we use multiple pid-caches'. Only one pid cache is
created during system startup and this used by processes that exist only in
init_pid_ns.When a process clones its pid namespace, we create additional pid caches as
necessary and use the pid cache to allocate 'struct pids' for that depth.Note, that with this patch the newly created namespace won't work, since the
rest of the kernel still uses global pids, but this is to be fixed soon. Init
pid namespace still works.[oleg@tv-sign.ru: merge fix]
Signed-off-by: Pavel Emelyanov
Signed-off-by: Sukadev Bhattiprolu
Cc: Paul Menage
Cc: "Eric W. Biederman"
Cc: Oleg Nesterov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
* remove pid.h from pid_namespaces.h;
* rework is_(cgroup|global)_init;
* optimize (get|put)_pid_ns for init_pid_ns;
* declare task_child_reaper to return actual reaper.Signed-off-by: Pavel Emelyanov
Cc: Oleg Nesterov
Cc: Sukadev Bhattiprolu
Cc: Paul Menage
Cc: "Eric W. Biederman"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
When searching the task by numerical id on may need to find it using global
pid (as it is done now in kernel) or by its virtual id, e.g. when sending a
signal to a task from one namespace the sender will specify the task's virtual
id and we should find the task by this value.[akpm@linux-foundation.org: fix gfs2 linkage]
Signed-off-by: Pavel Emelyanov
Cc: Oleg Nesterov
Cc: Sukadev Bhattiprolu
Cc: Paul Menage
Cc: "Eric W. Biederman"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
When showing pid to user or getting the pid numerical id for in-kernel use the
value of this id may differ depending on the namespace.This set of helpers is used to get the global pid nr, the virtual (i.e. seen
by task in its namespace) nr and the nr as it is seen from the specified
namespace.Signed-off-by: Pavel Emelyanov
Cc: Oleg Nesterov
Cc: Sukadev Bhattiprolu
Cc: Paul Menage
Cc: "Eric W. Biederman"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Each struct upid element of struct pid has to be initialized properly, i.e.
its nr mst be allocated from appropriate pidmap and ns set to appropriate
namespace.When allocating a new pid, we need to know the namespace this pid will live
in, so the additional argument is added to alloc_pid().On the other hand, the rest of the kernel still uses the pid->nr and
pid->pid_chain fields, so these ones are still initialized, but this will be
removed soon.Signed-off-by: Pavel Emelyanov
Cc: Oleg Nesterov
Cc: Sukadev Bhattiprolu
Cc: Paul Menage
Cc: "Eric W. Biederman"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Each namespace has a parent and is characterized by its "level". Level is the
number of the namespace generation. E.g. init namespace has level 0, after
cloning new one it will have level 1, the next one - 2 and so on and so forth.
This level is not explicitly limited.True hierarchy must have some way to find each namespace's children, but it is
not used in the patches, so this ability is not added (yet).Signed-off-by: Pavel Emelyanov
Cc: Oleg Nesterov
Cc: Sukadev Bhattiprolu
Cc: Paul Menage
Cc: "Eric W. Biederman"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
is_init() is an ambiguous name for the pid==1 check. Split it into
is_global_init() and is_container_init().A cgroup init has it's tsk->pid == 1.
A global init also has it's tsk->pid == 1 and it's active pid namespace
is the init_pid_ns. But rather than check the active pid namespace,
compare the task structure with 'init_pid_ns.child_reaper', which is
initialized during boot to the /sbin/init process and never changes.Changelog:
2.6.22-rc4-mm2-pidns1:
- Use 'init_pid_ns.child_reaper' to determine if a given task is the
global init (/sbin/init) process. This would improve performance
and remove dependence on the task_pid().2.6.21-mm2-pidns2:
- [Sukadev Bhattiprolu] Changed is_container_init() calls in {powerpc,
ppc,avr32}/traps.c for the _exception() call to is_global_init().
This way, we kill only the cgroup if the cgroup's init has a
bug rather than force a kernel panic.[akpm@linux-foundation.org: fix comment]
[sukadev@us.ibm.com: Use is_global_init() in arch/m32r/mm/fault.c]
[bunk@stusta.de: kernel/pid.c: remove unused exports]
[sukadev@us.ibm.com: Fix capability.c to work with threaded init]
Signed-off-by: Serge E. Hallyn
Signed-off-by: Sukadev Bhattiprolu
Acked-by: Pavel Emelianov
Cc: Eric W. Biederman
Cc: Cedric Le Goater
Cc: Dave Hansen
Cc: Herbert Poetzel
Cc: Kirill Korotaev
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
With multiple pid namespaces, a process is known by some pid_t in every
ancestor pid namespace. Every time the process forks, the child process also
gets a pid_t in every ancestor pid namespace.While a process is visible in >=1 pid namespaces, it can see pid_t's in only
one pid namespace. We call this pid namespace it's "active pid namespace",
and it is always the youngest pid namespace in which the process is known.This patch defines and uses a wrapper to find the active pid namespace of a
process. The implementation of the wrapper will be changed in when support
for multiple pid namespaces are added.Changelog:
2.6.22-rc4-mm2-pidns1:
- [Pavel Emelianov, Alexey Dobriyan] Back out the change to use
task_active_pid_ns() in child_reaper() since task->nsproxy
can be NULL during task exit (so child_reaper() continues to
use init_pid_ns).to implement child_reaper() since init_pid_ns.child_reaper to
implement child_reaper() since tsk->nsproxy can be NULL during exit.2.6.21-rc6-mm1:
- Rename task_pid_ns() to task_active_pid_ns() to reflect that a
process can have multiple pid namespaces.Signed-off-by: Sukadev Bhattiprolu
Acked-by: Pavel Emelianov
Cc: Eric W. Biederman
Cc: Cedric Le Goater
Cc: Dave Hansen
Cc: Serge Hallyn
Cc: Herbert Poetzel
Cc: Kirill Korotaev
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Add kmem_cache to pid_namespace to allocate pids from.
Since both implementations expand the struct pid to carry more numerical
values each namespace should have separate cache to store pids of different
sizes.Each kmem cache is name "pid_", where is the number of numerical ids
on the pid. Different namespaces with same level of nesting will have same
caches.This patch has two FIXMEs that are to be fixed after we reach the consensus
about the struct pid itself.The first one is that the namespace to free the pid from in free_pid() must be
taken from pid. Now the init_pid_ns is used.The second FIXME is about the cache allocation. When we do know how long the
object will be then we'll have to calculate this size in create_pid_cachep.
Right now the sizeof(struct pid) value is used.[akpm@linux-foundation.org: coding-style repair]
Signed-off-by: Pavel Emelianov
Acked-by: Cedric Le Goater
Acked-by: Sukadev Bhattiprolu
Cc: Kirill Korotaev
Cc: "Eric W. Biederman"
Cc: Herbert Poetzl
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
17 Jul, 2007
1 commit
-
While working on unshare support for the network namespace I noticed we
were putting clone flags in an int. Which is weird because the syscall
uses unsigned long and we at least need an unsigned to properly hold all of
the unshare flags.So to make the code consistent, this patch updates the code to use
unsigned long instead of int for the clone flags in those places
where we get it wrong today.Signed-off-by: Eric W. Biederman
Acked-by: Cedric Le Goater
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
11 May, 2007
2 commits
-
Statically initialize a struct pid for the swapper process (pid_t == 0) and
attach it to init_task. This is needed so task_pid(), task_pgrp() and
task_session() interfaces work on the swapper process also.Signed-off-by: Sukadev Bhattiprolu
Cc: Cedric Le Goater
Cc: Dave Hansen
Cc: Serge Hallyn
Cc: Eric Biederman
Cc: Herbert Poetzl
Cc:
Acked-by: Eric W. Biederman
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
attach_pid() currently takes a pid_t and then uses find_pid() to find the
corresponding struct pid. Sometimes we already have the struct pid. We can
then skip find_pid() if attach_pid() were to take a struct pid parameter.Signed-off-by: Sukadev Bhattiprolu
Cc: Cedric Le Goater
Cc: Dave Hansen
Cc: Serge Hallyn
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
09 May, 2007
1 commit
-
sys_clone() and sys_unshare() both makes copies of nsproxy and its associated
namespaces. But they have different code paths.This patch merges all the nsproxy and its associated namespace copy/clone
handling (as much as possible). Posted on container list earlier for
feedback.- Create a new nsproxy and its associated namespaces and pass it back to
caller to attach it to right process.- Changed all copy_*_ns() routines to return a new copy of namespace
instead of attaching it to task->nsproxy.- Moved the CAP_SYS_ADMIN checks out of copy_*_ns() routines.
- Removed unnessary !ns checks from copy_*_ns() and added BUG_ON()
just incase.- Get rid of all individual unshare_*_ns() routines and make use of
copy_*_ns() instead.[akpm@osdl.org: cleanups, warning fix]
[clg@fr.ibm.com: remove dup_namespaces() declaration]
[serue@us.ibm.com: fix CONFIG_IPC_NS=n, clone(CLONE_NEWIPC) retval]
[akpm@linux-foundation.org: fix build with CONFIG_SYSVIPC=n]
Signed-off-by: Badari Pulavarty
Signed-off-by: Serge Hallyn
Cc: Cedric Le Goater
Cc: "Eric W. Biederman"
Cc:
Signed-off-by: Cedric Le Goater
Cc: Oleg Nesterov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
08 May, 2007
1 commit
-
This patch provides a new macro
KMEM_CACHE(, )
to simplify slab creation. KMEM_CACHE creates a slab with the name of the
struct, with the size of the struct and with the alignment of the struct.
Additional slab flags may be specified if necessary.Example
struct test_slab {
int a,b,c;
struct list_head;
} __cacheline_aligned_in_smp;test_slab_cache = KMEM_CACHE(test_slab, SLAB_PANIC)
will create a new slab named "test_slab" of the size sizeof(struct
test_slab) and aligned to the alignment of test slab. If it fails then we
panic.Signed-off-by: Christoph Lameter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
31 Jan, 2007
1 commit
-
This is based on a patch by Eric W. Biederman, who pointed out that pid
namespaces are still fake, and we only have one ever active.So for the time being, we can modify any code which could access
tsk->nsproxy->pid_ns during task exit to just use &init_pid_ns instead,
and move the exit_task_namespaces call in do_exit() back above
exit_notify(), so that an exiting nfs server has a valid tsk->sighand to
work with.Long term, pulling pid_ns out of nsproxy might be the cleanest solution.
Signed-off-by: Eric W. Biederman
[ Eric's patch fixed to take care of free_pid() too ]
Signed-off-by: Serge E. Hallyn
Signed-off-by: Linus Torvalds
09 Dec, 2006
4 commits
-
Add a per pid_namespace child-reaper. This is needed so processes are reaped
within the same pid space and do not spill over to the parent pid space. Its
also needed so containers preserve existing semantic that pid == 1 would reap
orphaned children.This is based on Eric Biederman's patch: http://lkml.org/lkml/2006/2/6/285
Signed-off-by: Sukadev Bhattiprolu
Signed-off-by: Cedric Le Goater
Cc: Kirill Korotaev
Cc: Eric W. Biederman
Cc: Herbert Poetzl
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Signed-off-by: Cedric Le Goater
Cc: Kirill Korotaev
Cc: Eric W. Biederman
Cc: Herbert Poetzl
Cc: Sukadev Bhattiprolu
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Add the pid namespace framework to the nsproxy object. The copy of the pid
namespace only increases the refcount on the global pid namespace,
init_pid_ns, and unshare is not implemented.There is no configuration option to activate or deactivate this feature
because this not relevant for the moment.Signed-off-by: Cedric Le Goater
Cc: Kirill Korotaev
Cc: Eric W. Biederman
Cc: Herbert Poetzl
Cc: Sukadev Bhattiprolu
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Rename struct pspace to struct pid_namespace for consistency with other
namespaces (uts_namespace and ipc_namespace). Also rename
include/linux/pspace.h to include/linux/pid_namespace.h and variables from
pspace to pid_ns.Signed-off-by: Sukadev Bhattiprolu
Signed-off-by: Cedric Le Goater
Cc: Kirill Korotaev
Cc: Eric W. Biederman
Cc: Herbert Poetzl
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
08 Dec, 2006
1 commit
-
Replace all uses of kmem_cache_t with struct kmem_cache.
The patch was generated using the following script:
#!/bin/sh
#
# Replace one string by another in all the kernel sources.
#set -e
for file in `find * -name "*.c" -o -name "*.h"|xargs grep -l $1`; do
quilt add $file
sed -e "1,\$s/$1/$2/g" $file >/tmp/$$
mv /tmp/$$ $file
quilt refresh
doneThe script was run like this
sh replace kmem_cache_t "struct kmem_cache"
Signed-off-by: Christoph Lameter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
02 Oct, 2006
8 commits
-
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 -
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 -
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 -
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 -
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 -
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 -
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 -
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
27 Sep, 2006
2 commits
-
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 -
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
04 Jul, 2006
1 commit
-
cleanup: remove task_t and convert all the uses to struct task_struct. I
introduced it for the scheduler anno and it was a mistake.Conversion was mostly scripted, the result was reviewed and all
secondary whitespace and style impact (if any) was fixed up by hand.Signed-off-by: Ingo Molnar
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
01 Apr, 2006
1 commit
-
Simplifies the code, reduces the need for 4 pid hash tables, and makes the
code more capable.In the discussions I had with Oleg it was felt that to a large extent the
cleanup itself justified the work. With struct pid being dynamically
allocated meant we could create the hash table entry when the pid was
allocated and free the hash table entry when the pid was freed. Instead of
playing with the hash lists when ever a process would attach or detach to a
process.For myself the fact that it gave what my previous task_ref patch gave for free
with simpler code was a big win. The problem is that if you hold a reference
to struct task_struct you lock in 10K of low memory. If you do that in a user
controllable way like /proc does, with an unprivileged but hostile user space
application with typical resource limits of 1000 fds and 100 processes I can
trigger the OOM killer by consuming all of low memory with task structs, on a
machine wight 1GB of low memory.If I instead hold a reference to struct pid which holds a pointer to my
task_struct, I don't suffer from that problem because struct pid is 2 orders
of magnitude smaller. In fact struct pid is small enough that most other
kernel data structures dwarf it, so simply limiting the number of referring
data structures is enough to prevent exhaustion of low memory.This splits the current struct pid into two structures, struct pid and struct
pid_link, and reduces our number of hash tables from PIDTYPE_MAX to just one.
struct pid_link is the per process linkage into the hash tables and lives in
struct task_struct. struct pid is given an indepedent lifetime, and holds
pointers to each of the pid types.The independent life of struct pid simplifies attach_pid, and detach_pid,
because we are always manipulating the list of pids and not the hash table.
In addition in giving struct pid an indpendent life it makes the concept much
more powerful.Kernel data structures can now embed a struct pid * instead of a pid_t and
not suffer from pid wrap around problems or from keeping unnecessarily
large amounts of memory allocated.Signed-off-by: Eric W. Biederman
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
29 Mar, 2006
2 commits
-
fork_idle() does unhash_process() just after copy_process(). Contrary,
boot_cpu's idle thread explicitely registers itself for each pid_type with nr
= 0.copy_process() already checks p->pid != 0 before process_counts++, I think we
can just skip attach_pid() calls and job control inits for idle threads and
kill unhash_process(). We don't need to cleanup ->proc_dentry in fork_idle()
because with this patch idle threads are never hashed in
kernel/pid.c:pid_hash[].We don't need to hash pid == 0 in pidmap_init(). free_pidmap() is never
called with pid == 0 arg, so it will never be reused. So it is still possible
to use pid == 0 in any PIDTYPE_xxx namespace from kernel/pid.c's POV.However with this patch we don't hash pid == 0 for PIDTYPE_PID case. We still
have have PIDTYPE_PGID/PIDTYPE_SID entries with pid == 0: /sbin/init and
kernel threads which don't call daemonize().Signed-off-by: Oleg Nesterov
Cc: "Eric W. Biederman"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
switch_exec_pids is only called from de_thread by way of exec, and it is
only called when we are exec'ing from a non thread group leader.Currently switch_exec_pids gives the leader the pid of the thread and
unhashes and rehashes all of the process groups. The leader is already in
the EXIT_DEAD state so no one cares about it's pids. The only concern for
the leader is that __unhash_process called from release_task will function
correctly. If we don't touch the leader at all we know that
__unhash_process will work fine so there is no need to touch the leader.For the task becomming the thread group leader, we just need to give it the
pid of the old thread group leader, add it to the task list, and attach it
to the session and the process group of the thread group.Currently de_thread is also adding the task to the task list which is just
silly.Currently the only leader of __detach_pid besides detach_pid is
switch_exec_pids because of the ugly extra work that was being
performed.So this patch removes switch_exec_pids because it is doing too much, it is
creating an unnecessary special case in pid.c, duing work duplicated in
de_thread, and generally obscuring what it is going on.The necessary work is added to de_thread, and it seems to be a little
clearer there what is going on.Signed-off-by: Eric W. Biederman
Cc: Oleg Nesterov
Cc: Kirill Korotaev
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds