Hi,

Shrink task_struct by replacing the notifier callback with a
notifier list. The block_all_signals() function (and the signal
notifier mechanism) has only one user at the moment, which is drm.

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: 2615, holes: 3, sum holes: 9 */
   /* bit holes: 2, sum bit holes: 62 bits */
   /* paddings: 1, sum paddings: 8 */

x86_64 before:

   /* size: 3648, cachelines: 57 */
   /* sum members: 3587, holes: 13, sum holes: 53 */
   /* bit holes: 2, sum bit holes: 62 bits */
   /* padding: 8 */

x86_64 after:

   /* size: 3632, cachelines: 57 */
   /* sum members: 3579, holes: 13, sum holes: 53 */
   /* bit holes: 2, sum bit holes: 62 bits */
   /* last cacheline: 48 bytes */

Signed-off-by: Davi E. M. Arnaut <[EMAIL PROTECTED]>

---
 drivers/char/drm/drmP.h     |    4 ++--
 drivers/char/drm/drm_lock.c |   16 +++++++++-------
 include/linux/init_task.h   |    1 +
 include/linux/sched.h       |   12 +++++-------
 include/linux/signal.h      |   16 ++++++++++++++++
 kernel/fork.c               |    1 +
 kernel/signal.c             |   42 ++++++++++++++++++++----------------------
 7 files changed, 54 insertions(+), 38 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;
-       
+       /* signal notifier list */
+       struct list_head notifier_list;
+
        void *security;
        struct audit_context *audit_context;
        seccomp_t seccomp;
@@ -1339,9 +1338,8 @@ 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 block_signals(struct signal_notifier *);
+extern void unblock_signals(struct signal_notifier *);
 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}},                                        \
+       .notifier_list  = LIST_HEAD_INIT(tsk.notifier_list),            \
        .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 +27,22 @@ struct sigpending {
        sigset_t signal;
 };
 
+/**
+ * struct signal_notifier - the signal notifier struct
+ * @list: list head 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 list_head list;
+       int (*func)(void *priv);
+       void *data;
+       sigset_t mask;
+};
+
 /*
  * 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_LIST_HEAD(&p->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;
+       block_signals(&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();
+       unblock_signals(&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
@@ -242,32 +242,28 @@ flush_signal_handlers(struct task_struct
  * 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.  */
+ * the signal will be blocked.
+ */
 
 void
-block_all_signals(int (*notifier)(void *priv), void *priv, sigset_t *mask)
+block_signals(struct signal_notifier *notifier)
 {
        unsigned long flags;
 
        spin_lock_irqsave(&current->sighand->siglock, flags);
-       current->notifier_mask = mask;
-       current->notifier_data = priv;
-       current->notifier = notifier;
+       list_add_tail(&notifier->list, &current->notifier_list);
        spin_unlock_irqrestore(&current->sighand->siglock, flags);
 }
 
 /* Notify the system that blocking has ended. */
 
 void
-unblock_all_signals(void)
+unblock_signals(struct signal_notifier *notifier)
 {
        unsigned long flags;
 
        spin_lock_irqsave(&current->sighand->siglock, flags);
-       current->notifier = NULL;
-       current->notifier_data = NULL;
+       list_del(&notifier->list);
        recalc_sigpending();
        spin_unlock_irqrestore(&current->sighand->siglock, flags);
 }
@@ -318,22 +314,24 @@ static int collect_signal(int sig, struc
 static int __dequeue_signal(struct sigpending *pending, sigset_t *mask,
                        siginfo_t *info)
 {
+       struct signal_notifier *tmp, *notifier;
        int sig = next_signal(pending, mask);
 
-       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;
+
+       list_for_each_entry_safe(notifier, tmp, &current->notifier_list, list) {
+               if (sigismember(&notifier->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 +1858,8 @@ 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(block_signals);
+EXPORT_SYMBOL(unblock_signals);
 
 
 /*
-
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