[PATCH v2 1/3] kernel: pid: Update documentation.

[Varsha Rao <rvarsha016@gmail.com>]

This patch adds comments to update documentation.

Signed-off-by: Varsha Rao <rvarsha016@gmail.com>
---
Changes in v2:
- No change.

 kernel/pid.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/kernel/pid.c b/kernel/pid.c
index 0143ac0..0b0aad4 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -43,6 +43,7 @@
 #define pid_hashfn(nr, ns)	\
 	hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift)
 static struct hlist_head *pid_hash;
+/* Doubly linked hash lists to find PID in given namespace. */
 static unsigned int pidhash_shift = 4;
 struct pid init_struct_pid = INIT_STRUCT_PID;
 
@@ -53,6 +54,7 @@ int pid_max = PID_MAX_DEFAULT;
 int pid_max_min = RESERVED_PIDS + 1;
 int pid_max_max = PID_MAX_LIMIT;
 
+/* mk_pid() returns distance between map and offset pidmap. */
 static inline int mk_pid(struct pid_namespace *pid_ns,
 		struct pidmap *map, int off)
 {
@@ -101,6 +103,7 @@ EXPORT_SYMBOL_GPL(init_pid_ns);
 
 static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(pidmap_lock);
 
+/* free_pidmap() : It frees process id. */
 static void free_pidmap(struct upid *upid)
 {
 	int nr = upid->nr;
@@ -150,6 +153,9 @@ static void set_last_pid(struct pid_namespace *pid_ns, int base, int pid)
 	} while ((prev != last_write) && (pid_before(base, last_write, pid)));
 }
 
+/* alloc_pidmap(): Increments last pid by one and returns it if new pid
+ * is valid.
+ */
 static int alloc_pidmap(struct pid_namespace *pid_ns)
 {
 	int i, offset, max_scan, pid, last = pid_ns->last_pid;
@@ -212,6 +218,9 @@ static int alloc_pidmap(struct pid_namespace *pid_ns)
 	return -EAGAIN;
 }
 
+/* next_pidmap() is used to find the first pid which is greater than previous
+ * last allocated pid.
+ */
 int next_pidmap(struct pid_namespace *pid_ns, unsigned int last)
 {
 	int offset;
@@ -233,6 +242,7 @@ int next_pidmap(struct pid_namespace *pid_ns, unsigned int last)
 	return -1;
 }
 
+/* put_pid() checks whether pid can be reallocated. */
 void put_pid(struct pid *pid)
 {
 	struct pid_namespace *ns;
@@ -249,6 +259,9 @@ void put_pid(struct pid *pid)
 }
 EXPORT_SYMBOL_GPL(put_pid);
 
+/* delayed_put_pid(): Finds the real location of struct pid in the
+ * memory and checks whether it can be reallocated with put_pid().
+ */
 static void delayed_put_pid(struct rcu_head *rhp)
 {
 	struct pid *pid = container_of(rhp, struct pid, rcu);
@@ -293,6 +306,9 @@ void free_pid(struct pid *pid)
 	call_rcu(&pid->rcu, delayed_put_pid);
 }
 
+/* alloc_pid(): Allocates local pid for each multiple namespaces
+ * in which new process created is visible.
+ */
 struct pid *alloc_pid(struct pid_namespace *ns)
 {
 	struct pid *pid;
-- 
2.9.3