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Date: Mon, 21 May 2007 17:47:33 +0100
From: "Dave Airlie" <airlied@...il.com>
To: "Davi Arnaut" <davi@...ent.com.br>
Cc: "Christoph Hellwig" <hch@...radead.org>,
"Andrew Morton" <akpm@...ux-foundation.org>,
"Linus Torvalds" <torvalds@...ux-foundation.org>,
"Dave Airlie" <airlied@...ux.ie>,
"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] shrink task_struct by 16 bytes
>
> Shrink task_struct by replacing the notifier callback with a notifier
> list that allows for multiple clients to register notifiers. It also
> saves one cacheline on i386.
>
> The patch also renames the un/block_all_signals() functions to more
> descriptive names signal_notifier_add/del() and updates the kerneldoc
> comments accordingly. The only in-tree user (drm) is converted.
>
> Thanks to Christoph Hellwig for useful comments and review.
>
> Pahole output for task_struct:
>
> i386 before:
>
> /* size: 2640, cachelines: 42 */
> /* sum members: 2619, holes: 3, sum holes: 9 */
> /* bit holes: 2, sum bit holes: 62 bits */
> /* padding: 12 */
> /* paddings: 1, sum paddings: 8 */
> /* last cacheline: 16 bytes */
>
> i386 after:
>
> /* size: 2624, cachelines: 41 */
> /* sum members: 2611, holes: 3, sum holes: 9 */
> /* bit holes: 2, sum bit holes: 62 bits */
> /* padding: 4 */
> /* paddings: 1, sum paddings: 8 */
>
> x86_64 before:
>
> /* size: 3632, cachelines: 57 */
> /* sum members: 3579, holes: 10, sum holes: 45 */
> /* bit holes: 2, sum bit holes: 62 bits */
> /* padding: 8 */
> /* last cacheline: 48 bytes */
>
> x86_64 after:
>
> /* size: 3616, cachelines: 57 */
> /* sum members: 3563, holes: 10, sum holes: 45 */
> /* bit holes: 2, sum bit holes: 62 bits */
> /* padding: 8 */
> /* last cacheline: 32 bytes */
>
> Signed-off-by: Davi E. M. Arnaut <davi@...ent.com.br>
> Cc: Dave Airlie <airlied@...ux.ie>
Signed-off-by: Dave Airlie <airlied@...ux.ie>
No problems from me either..
Dave.
> Cc: Christoph Hellwig <hch@...radead.org>
>
> ---
> drivers/char/drm/drmP.h | 4 +-
> drivers/char/drm/drm_lock.c | 16 ++++++----
> include/linux/init_task.h | 1
> include/linux/sched.h | 10 ++----
> include/linux/signal.h | 21 ++++++++++++++
> kernel/fork.c | 1
> kernel/signal.c | 66 ++++++++++++++++++++++----------------------
> 7 files changed, 71 insertions(+), 48 deletions(-)
>
> Index: linux-2.6/include/linux/sched.h
> ===================================================================
> --- linux-2.6.orig/include/linux/sched.h
> +++ linux-2.6/include/linux/sched.h
> @@ -963,10 +963,9 @@ struct task_struct {
>
> unsigned long sas_ss_sp;
> size_t sas_ss_size;
> - int (*notifier)(void *priv);
> - void *notifier_data;
> - sigset_t *notifier_mask;
> -
> + /* struct signal_notifier callback list */
> + struct hlist_head signal_notifier_list;
> +
> void *security;
> struct audit_context *audit_context;
> seccomp_t seccomp;
> @@ -1339,9 +1338,6 @@ static inline int dequeue_signal_lock(st
> return ret;
> }
>
> -extern void block_all_signals(int (*notifier)(void *priv), void *priv,
> - sigset_t *mask);
> -extern void unblock_all_signals(void);
> extern void release_task(struct task_struct * p);
> extern int send_sig_info(int, struct siginfo *, struct task_struct *);
> extern int send_group_sig_info(int, struct siginfo *, struct task_struct *);
> Index: linux-2.6/include/linux/init_task.h
> ===================================================================
> --- linux-2.6.orig/include/linux/init_task.h
> +++ linux-2.6/include/linux/init_task.h
> @@ -157,6 +157,7 @@ extern struct group_info init_groups;
> .list = LIST_HEAD_INIT(tsk.pending.list), \
> .signal = {{0}}}, \
> .blocked = {{0}}, \
> + .signal_notifier_list = HLIST_HEAD_INIT, \
> .alloc_lock = __SPIN_LOCK_UNLOCKED(tsk.alloc_lock), \
> .journal_info = NULL, \
> .cpu_timers = INIT_CPU_TIMERS(tsk.cpu_timers), \
> Index: linux-2.6/include/linux/signal.h
> ===================================================================
> --- linux-2.6.orig/include/linux/signal.h
> +++ linux-2.6/include/linux/signal.h
> @@ -27,6 +27,27 @@ struct sigpending {
> sigset_t signal;
> };
>
> +/**
> + * struct signal_notifier - the signal notifier struct
> + * @node: hash list node to enqueue into the process notifier list
> + * @func: notifier callback function. if the callback routine returns 0
> + * then then signal will be blocked.
> + * @data: pointer to private data that the notifier routine can use to
> + * determine if the signal should be blocked or not.
> + * @mask: mask of signals to call the callback routine upon
> + */
> +struct signal_notifier {
> + struct hlist_node node;
> + int (*func)(void *priv);
> + void *data;
> + sigset_t mask;
> +};
> +
> +/* Add a signal notifier struct to the current process notifier list */
> +extern void signal_notifier_add(struct signal_notifier *);
> +/* Remove a signal notifier struct from the current process notifier list */
> +extern void signal_notifier_del(struct signal_notifier *);
> +
> /*
> * Define some primitives to manipulate sigset_t.
> */
> Index: linux-2.6/kernel/fork.c
> ===================================================================
> --- linux-2.6.orig/kernel/fork.c
> +++ linux-2.6/kernel/fork.c
> @@ -1034,6 +1034,7 @@ static struct task_struct *copy_process(
> p->vfork_done = NULL;
> spin_lock_init(&p->alloc_lock);
>
> + INIT_HLIST_HEAD(&p->signal_notifier_list);
> clear_tsk_thread_flag(p, TIF_SIGPENDING);
> init_sigpending(&p->pending);
>
> Index: linux-2.6/drivers/char/drm/drm_lock.c
> ===================================================================
> --- linux-2.6.orig/drivers/char/drm/drm_lock.c
> +++ linux-2.6/drivers/char/drm/drm_lock.c
> @@ -110,14 +110,16 @@ int drm_lock(struct inode *inode, struct
> DRM_DEBUG( "%d %s\n", lock.context, ret ? "interrupted" : "has lock" );
> if (ret) return ret;
>
> - sigemptyset(&dev->sigmask);
> - sigaddset(&dev->sigmask, SIGSTOP);
> - sigaddset(&dev->sigmask, SIGTSTP);
> - sigaddset(&dev->sigmask, SIGTTIN);
> - sigaddset(&dev->sigmask, SIGTTOU);
> + sigemptyset(&dev->notifier.mask);
> + sigaddset(&dev->notifier.mask, SIGSTOP);
> + sigaddset(&dev->notifier.mask, SIGTSTP);
> + sigaddset(&dev->notifier.mask, SIGTTIN);
> + sigaddset(&dev->notifier.mask, SIGTTOU);
> dev->sigdata.context = lock.context;
> dev->sigdata.lock = dev->lock.hw_lock;
> - block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
> + dev->notifier.data = &dev->sigdata;
> + dev->notifier.func = drm_notifier;
> + signal_notifier_add(&dev->notifier);
>
> if (dev->driver->dma_ready && (lock.flags & _DRM_LOCK_READY))
> dev->driver->dma_ready(dev);
> @@ -189,7 +191,7 @@ int drm_unlock(struct inode *inode, stru
> }
> }
>
> - unblock_all_signals();
> + signal_notifier_del(&dev->notifier);
> return 0;
> }
>
> Index: linux-2.6/drivers/char/drm/drmP.h
> ===================================================================
> --- linux-2.6.orig/drivers/char/drm/drmP.h
> +++ linux-2.6/drivers/char/drm/drmP.h
> @@ -750,8 +750,8 @@ typedef struct drm_device {
> drm_sg_mem_t *sg; /**< Scatter gather memory */
> unsigned long *ctx_bitmap; /**< context bitmap */
> void *dev_private; /**< device private data */
> - drm_sigdata_t sigdata; /**< For block_all_signals */
> - sigset_t sigmask;
> + drm_sigdata_t sigdata; /**< Signal notifier data */
> + struct signal_notifier notifier; /**< For block_signals */
>
> struct drm_driver *driver;
> drm_local_map_t *agp_buffer_map;
> Index: linux-2.6/kernel/signal.c
> ===================================================================
> --- linux-2.6.orig/kernel/signal.c
> +++ linux-2.6/kernel/signal.c
> @@ -237,37 +237,35 @@ flush_signal_handlers(struct task_struct
> }
> }
>
> -
> -/* Notify the system that a driver wants to block all signals for this
> - * process, and wants to be notified if any signals at all were to be
> - * sent/acted upon. If the notifier routine returns non-zero, then the
> - * signal will be acted upon after all. If the notifier routine returns 0,
> - * then then signal will be blocked. Only one block per process is
> - * allowed. priv is a pointer to private data that the notifier routine
> - * can use to determine if the signal should be blocked or not. */
> -
> -void
> -block_all_signals(int (*notifier)(void *priv), void *priv, sigset_t *mask)
> +/**
> + * signal_notifier_add - Add a signal notifier callback to the current process
> + * @notifier: the signal_notifier struct to add
> + *
> + * Notify the system that a driver wants to block a set of signals for this
> + * process and wants to be notified if any signals at all were to be sent or
> + * acted upon. If the notifier routine returns non-zero, then the signal will
> + * be acted upon after all. If the notifier routine returns 0, the signal will
> + * be blocked.
> + */
> +void signal_notifier_add(struct signal_notifier *notifier)
> {
> unsigned long flags;
>
> spin_lock_irqsave(¤t->sighand->siglock, flags);
> - current->notifier_mask = mask;
> - current->notifier_data = priv;
> - current->notifier = notifier;
> + hlist_add_head(¬ifier->node, ¤t->signal_notifier_list);
> spin_unlock_irqrestore(¤t->sighand->siglock, flags);
> }
>
> -/* Notify the system that blocking has ended. */
> -
> -void
> -unblock_all_signals(void)
> +/**
> + * signal_notifier_del - Notify the system that blocking has ended
> + * @notifier: the signal_notifier struct to remove
> + */
> +void signal_notifier_del(struct signal_notifier *notifier)
> {
> unsigned long flags;
>
> spin_lock_irqsave(¤t->sighand->siglock, flags);
> - current->notifier = NULL;
> - current->notifier_data = NULL;
> + hlist_del(¬ifier->node);
> recalc_sigpending();
> spin_unlock_irqrestore(¤t->sighand->siglock, flags);
> }
> @@ -318,22 +316,26 @@ static int collect_signal(int sig, struc
> static int __dequeue_signal(struct sigpending *pending, sigset_t *mask,
> siginfo_t *info)
> {
> + struct hlist_node *entry, *next;
> + struct signal_notifier *notifier;
> int sig = next_signal(pending, mask);
> + struct hlist_head *hash_list = ¤t->signal_notifier_list;
>
> - if (sig) {
> - if (current->notifier) {
> - if (sigismember(current->notifier_mask, sig)) {
> - if (!(current->notifier)(current->notifier_data)) {
> - clear_thread_flag(TIF_SIGPENDING);
> - return 0;
> - }
> + if (unlikely(!sig))
> + return 0;
> +
> + hlist_for_each_entry_safe(notifier, entry, next, hash_list, node) {
> + if (sigismember(¬ifier->mask, sig)) {
> + if (!notifier->func(notifier->data)) {
> + clear_thread_flag(TIF_SIGPENDING);
> + return 0;
> }
> }
> -
> - if (!collect_signal(sig, pending, info))
> - sig = 0;
> }
>
> + if (!collect_signal(sig, pending, info))
> + sig = 0;
> +
> return sig;
> }
>
> @@ -1860,8 +1862,8 @@ EXPORT_SYMBOL(ptrace_notify);
> EXPORT_SYMBOL(send_sig);
> EXPORT_SYMBOL(send_sig_info);
> EXPORT_SYMBOL(sigprocmask);
> -EXPORT_SYMBOL(block_all_signals);
> -EXPORT_SYMBOL(unblock_all_signals);
> +EXPORT_SYMBOL(signal_notifier_add);
> +EXPORT_SYMBOL(signal_notifier_del);
>
>
> /*
> -
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