statically initialize struct pid for swapper

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 <sukadev@us.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: <containers@lists.osdl.org>
Acked-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 45170b2..a68835f 100644 (file)
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -88,6 +88,28 @@ extern struct nsproxy init_nsproxy;
 
 extern struct group_info init_groups;
 
+#define INIT_STRUCT_PID {                                              \
+       .count          = ATOMIC_INIT(1),                               \
+       .nr             = 0,                                            \
+       /* Don't put this struct pid in pid_hash */                     \
+       .pid_chain      = { .next = NULL, .pprev = NULL },              \
+       .tasks          = {                                             \
+               { .first = &init_task.pids[PIDTYPE_PID].node },         \
+               { .first = &init_task.pids[PIDTYPE_PGID].node },        \
+               { .first = &init_task.pids[PIDTYPE_SID].node },         \
+       },                                                              \
+       .rcu            = RCU_HEAD_INIT,                                \
+}
+
+#define INIT_PID_LINK(type)                                    \
+{                                                              \
+       .node = {                                               \
+               .next = NULL,                                   \
+               .pprev = &init_struct_pid.tasks[type].first,    \
+       },                                                      \
+       .pid = &init_struct_pid,                                \
+}
+
 /*
  *  INIT_TASK is used to set up the first task table, touch at
  * your own risk!. Base=0, limit=0x1fffff (=2MB)
@@ -139,6 +161,11 @@ extern struct group_info init_groups;
        .cpu_timers     = INIT_CPU_TIMERS(tsk.cpu_timers),              \
        .fs_excl        = ATOMIC_INIT(0),                               \
        .pi_lock        = __SPIN_LOCK_UNLOCKED(tsk.pi_lock),            \
+       .pids = {                                                       \
+               [PIDTYPE_PID]  = INIT_PID_LINK(PIDTYPE_PID),            \
+               [PIDTYPE_PGID] = INIT_PID_LINK(PIDTYPE_PGID),           \
+               [PIDTYPE_SID]  = INIT_PID_LINK(PIDTYPE_SID),            \
+       },                                                              \
        INIT_TRACE_IRQFLAGS                                             \
        INIT_LOCKDEP                                                    \
 }

diff --git a/include/linux/pid.h b/include/linux/pid.h
index 33d3438..1e0e4e3 100644 (file)
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -51,6 +51,8 @@ struct pid
        struct rcu_head rcu;
 };
 
+extern struct pid init_struct_pid;
+
 struct pid_link
 {
        struct hlist_node node;

diff --git a/kernel/pid.c b/kernel/pid.c
index d76f593..eb66bd2 100644 (file)
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -27,11 +27,13 @@
 #include <linux/bootmem.h>
 #include <linux/hash.h>
 #include <linux/pid_namespace.h>
+#include <linux/init_task.h>
 
 #define pid_hashfn(nr) hash_long((unsigned long)nr, pidhash_shift)
 static struct hlist_head *pid_hash;
 static int pidhash_shift;
 static struct kmem_cache *pid_cachep;
+struct pid init_struct_pid = INIT_STRUCT_PID;
 
 int pid_max = PID_MAX_DEFAULT;