From: "Carlos R. Mafra" As git-grep shows, open_softirq() is always called with the last argument being NULL block/blk-core.c: open_softirq(BLOCK_SOFTIRQ, blk_done_softirq, NULL); kernel/hrtimer.c: open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq, NULL); kernel/rcuclassic.c: open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL); kernel/rcupreempt.c: open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL); kernel/sched.c: open_softirq(SCHED_SOFTIRQ, run_rebalance_domains, NULL); kernel/softirq.c: open_softirq(TASKLET_SOFTIRQ, tasklet_action, NULL); kernel/softirq.c: open_softirq(HI_SOFTIRQ, tasklet_hi_action, NULL); kernel/timer.c: open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL); net/core/dev.c: open_softirq(NET_TX_SOFTIRQ, net_tx_action, NULL); net/core/dev.c: open_softirq(NET_RX_SOFTIRQ, net_rx_action, NULL); This observation has already been made by Matthew Wilcox in June 2002 (http://www.cs.helsinki.fi/linux/linux-kernel/2002-25/0687.html) "I notice that none of the current softirq routines use the data element passed to them." and the situation hasn't changed since them. So it appears we can safely remove that extra argument to save 128 (54) bytes of kernel data (text). Signed-off-by: Carlos R. Mafra Cc: Ingo Molnar Cc: David S. Miller Cc: Thomas Gleixner Cc: Jens Axboe Cc: "Paul E. McKenney" Reviewed-by: Matthew Wilcox Signed-off-by: Andrew Morton --- block/blk-core.c | 2 +- include/linux/interrupt.h | 3 +-- kernel/hrtimer.c | 2 +- kernel/rcuclassic.c | 2 +- kernel/rcupreempt.c | 2 +- kernel/sched.c | 2 +- kernel/softirq.c | 7 +++---- kernel/timer.c | 2 +- net/core/dev.c | 4 ++-- 9 files changed, 12 insertions(+), 14 deletions(-) diff -puN block/blk-core.c~remove-argument-from-open_softirq-which-is-always-null block/blk-core.c --- a/block/blk-core.c~remove-argument-from-open_softirq-which-is-always-null +++ a/block/blk-core.c @@ -2042,7 +2042,7 @@ int __init blk_dev_init(void) for_each_possible_cpu(i) INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i)); - open_softirq(BLOCK_SOFTIRQ, blk_done_softirq, NULL); + open_softirq(BLOCK_SOFTIRQ, blk_done_softirq); register_hotcpu_notifier(&blk_cpu_notifier); return 0; diff -puN include/linux/interrupt.h~remove-argument-from-open_softirq-which-is-always-null include/linux/interrupt.h --- a/include/linux/interrupt.h~remove-argument-from-open_softirq-which-is-always-null +++ a/include/linux/interrupt.h @@ -285,12 +285,11 @@ enum struct softirq_action { void (*action)(struct softirq_action *); - void *data; }; asmlinkage void do_softirq(void); asmlinkage void __do_softirq(void); -extern void open_softirq(int nr, void (*action)(struct softirq_action*), void *data); +extern void open_softirq(int nr, void (*action)(struct softirq_action *)); extern void softirq_init(void); #define __raise_softirq_irqoff(nr) do { or_softirq_pending(1UL << (nr)); } while (0) extern void raise_softirq_irqoff(unsigned int nr); diff -puN kernel/hrtimer.c~remove-argument-from-open_softirq-which-is-always-null kernel/hrtimer.c --- a/kernel/hrtimer.c~remove-argument-from-open_softirq-which-is-always-null +++ a/kernel/hrtimer.c @@ -1669,7 +1669,7 @@ void __init hrtimers_init(void) (void *)(long)smp_processor_id()); register_cpu_notifier(&hrtimers_nb); #ifdef CONFIG_HIGH_RES_TIMERS - open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq, NULL); + open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq); #endif } diff -puN kernel/rcuclassic.c~remove-argument-from-open_softirq-which-is-always-null kernel/rcuclassic.c --- a/kernel/rcuclassic.c~remove-argument-from-open_softirq-which-is-always-null +++ a/kernel/rcuclassic.c @@ -557,7 +557,7 @@ static void __cpuinit rcu_online_cpu(int rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp); rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp); - open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL); + open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); } static int __cpuinit rcu_cpu_notify(struct notifier_block *self, diff -puN kernel/rcupreempt.c~remove-argument-from-open_softirq-which-is-always-null kernel/rcupreempt.c --- a/kernel/rcupreempt.c~remove-argument-from-open_softirq-which-is-always-null +++ a/kernel/rcupreempt.c @@ -1443,7 +1443,7 @@ void __init __rcu_init(void) for_each_online_cpu(cpu) rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long) cpu); - open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL); + open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); } /* diff -puN kernel/sched.c~remove-argument-from-open_softirq-which-is-always-null kernel/sched.c --- a/kernel/sched.c~remove-argument-from-open_softirq-which-is-always-null +++ a/kernel/sched.c @@ -8152,7 +8152,7 @@ void __init sched_init(void) #endif #ifdef CONFIG_SMP - open_softirq(SCHED_SOFTIRQ, run_rebalance_domains, NULL); + open_softirq(SCHED_SOFTIRQ, run_rebalance_domains); #endif #ifdef CONFIG_RT_MUTEXES diff -puN kernel/softirq.c~remove-argument-from-open_softirq-which-is-always-null kernel/softirq.c --- a/kernel/softirq.c~remove-argument-from-open_softirq-which-is-always-null +++ a/kernel/softirq.c @@ -347,9 +347,8 @@ void raise_softirq(unsigned int nr) local_irq_restore(flags); } -void open_softirq(int nr, void (*action)(struct softirq_action*), void *data) +void open_softirq(int nr, void (*action)(struct softirq_action *)) { - softirq_vec[nr].data = data; softirq_vec[nr].action = action; } @@ -503,8 +502,8 @@ void __init softirq_init(void) &per_cpu(tasklet_hi_vec, cpu).head; } - open_softirq(TASKLET_SOFTIRQ, tasklet_action, NULL); - open_softirq(HI_SOFTIRQ, tasklet_hi_action, NULL); + open_softirq(TASKLET_SOFTIRQ, tasklet_action); + open_softirq(HI_SOFTIRQ, tasklet_hi_action); } static int ksoftirqd(void * __bind_cpu) diff -puN kernel/timer.c~remove-argument-from-open_softirq-which-is-always-null kernel/timer.c --- a/kernel/timer.c~remove-argument-from-open_softirq-which-is-always-null +++ a/kernel/timer.c @@ -1494,7 +1494,7 @@ void __init init_timers(void) BUG_ON(err == NOTIFY_BAD); register_cpu_notifier(&timers_nb); - open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL); + open_softirq(TIMER_SOFTIRQ, run_timer_softirq); } /** diff -puN net/core/dev.c~remove-argument-from-open_softirq-which-is-always-null net/core/dev.c --- a/net/core/dev.c~remove-argument-from-open_softirq-which-is-always-null +++ a/net/core/dev.c @@ -4563,8 +4563,8 @@ static int __init net_dev_init(void) dev_boot_phase = 0; - open_softirq(NET_TX_SOFTIRQ, net_tx_action, NULL); - open_softirq(NET_RX_SOFTIRQ, net_rx_action, NULL); + open_softirq(NET_TX_SOFTIRQ, net_tx_action); + open_softirq(NET_RX_SOFTIRQ, net_rx_action); hotcpu_notifier(dev_cpu_callback, 0); dst_init(); diff -puN /dev/null /dev/null _