Introduce a handy list_first_entry macro

There are many places in the kernel where the construction like

   foo = list_entry(head->next, struct foo_struct, list);

are used.
The code might look more descriptive and neat if using the macro

   list_first_entry(head, type, member) \
             list_entry((head)->next, type, member)

Here is the macro itself and the examples of its usage in the generic code.
 If it will turn out to be useful, I can prepare the set of patches to
inject in into arch-specific code, drivers, networking, etc.

Signed-off-by: Pavel Emelianov <xemul@openvz.org>
Signed-off-by: Kirill Korotaev <dev@openvz.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Zach Brown <zach.brown@oracle.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: John McCutchan <ttb@tentacle.dhs.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 9 insertions, 9 deletions

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 657f77697415..1de710e18373 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -971,7 +971,7 @@ static void check_thread_timers(struct task_struct *tsk,
         maxfire = 20;
         tsk->it_prof_expires = cputime_zero;
         while (!list_empty(timers)) {
-                struct cpu_timer_list *t = list_entry(timers->next,
+                struct cpu_timer_list *t = list_first_entry(timers,
                                                       struct cpu_timer_list,
                                                       entry);
                 if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
@@ -986,7 +986,7 @@ static void check_thread_timers(struct task_struct *tsk,
         maxfire = 20;
         tsk->it_virt_expires = cputime_zero;
         while (!list_empty(timers)) {
-                struct cpu_timer_list *t = list_entry(timers->next,
+                struct cpu_timer_list *t = list_first_entry(timers,
                                                       struct cpu_timer_list,
                                                       entry);
                 if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
@@ -1001,7 +1001,7 @@ static void check_thread_timers(struct task_struct *tsk,
         maxfire = 20;
         tsk->it_sched_expires = 0;
         while (!list_empty(timers)) {
-                struct cpu_timer_list *t = list_entry(timers->next,
+                struct cpu_timer_list *t = list_first_entry(timers,
                                                       struct cpu_timer_list,
                                                       entry);
                 if (!--maxfire || tsk->sched_time < t->expires.sched) {
@@ -1057,7 +1057,7 @@ static void check_process_timers(struct task_struct *tsk,
         maxfire = 20;
         prof_expires = cputime_zero;
         while (!list_empty(timers)) {
-                struct cpu_timer_list *t = list_entry(timers->next,
+                struct cpu_timer_list *t = list_first_entry(timers,
                                                       struct cpu_timer_list,
                                                       entry);
                 if (!--maxfire || cputime_lt(ptime, t->expires.cpu)) {
@@ -1072,7 +1072,7 @@ static void check_process_timers(struct task_struct *tsk,
         maxfire = 20;
         virt_expires = cputime_zero;
         while (!list_empty(timers)) {
-                struct cpu_timer_list *t = list_entry(timers->next,
+                struct cpu_timer_list *t = list_first_entry(timers,
                                                       struct cpu_timer_list,
                                                       entry);
                 if (!--maxfire || cputime_lt(utime, t->expires.cpu)) {
@@ -1087,7 +1087,7 @@ static void check_process_timers(struct task_struct *tsk,
         maxfire = 20;
         sched_expires = 0;
         while (!list_empty(timers)) {
-                struct cpu_timer_list *t = list_entry(timers->next,
+                struct cpu_timer_list *t = list_first_entry(timers,
                                                       struct cpu_timer_list,
                                                       entry);
                 if (!--maxfire || sched_time < t->expires.sched) {
@@ -1400,7 +1400,7 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
          */
         head = &tsk->signal->cpu_timers[clock_idx];
         if (list_empty(head) ||
-            cputime_ge(list_entry(head->next,
+            cputime_ge(list_first_entry(head,
                                   struct cpu_timer_list, entry)->expires.cpu,
                        *newval)) {
                 /*
diff --git a/kernel/timer.c b/kernel/timer.c
index ba41af2bb6cc..7a6448340f90 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -629,7 +629,7 @@ static inline void __run_timers(tvec_base_t *base)
                         void (*fn)(unsigned long);
                         unsigned long data;
 
-                        timer = list_entry(head->next,struct timer_list,entry);
+                        timer = list_first_entry(head, struct timer_list,entry);
                         fn = timer->function;
                         data = timer->data;
 
@@ -1248,7 +1248,7 @@ static void migrate_timer_list(tvec_base_t *new_base, struct list_head *head)
         struct timer_list *timer;
 
         while (!list_empty(head)) {
-                timer = list_entry(head->next, struct timer_list, entry);
+                timer = list_first_entry(head, struct timer_list, entry);
                 detach_timer(timer, 0);
                 timer_set_base(timer, new_base);
                 internal_add_timer(new_base, timer);