diff options
Diffstat (limited to 'kernel/sys.c')
| -rw-r--r-- | kernel/sys.c | 81 |
1 files changed, 40 insertions, 41 deletions
diff --git a/kernel/sys.c b/kernel/sys.c index 0b6ec0e7936..dbb3b9c7ea6 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -4,7 +4,6 @@ * Copyright (C) 1991, 1992 Linus Torvalds */ -#include <linux/config.h> #include <linux/module.h> #include <linux/mm.h> #include <linux/utsname.h> @@ -13,7 +12,6 @@ #include <linux/notifier.h> #include <linux/reboot.h> #include <linux/prctl.h> -#include <linux/init.h> #include <linux/highuid.h> #include <linux/fs.h> #include <linux/kernel.h> @@ -57,6 +55,12 @@ #ifndef GET_FPEXC_CTL # define GET_FPEXC_CTL(a,b) (-EINVAL) #endif +#ifndef GET_ENDIAN +# define GET_ENDIAN(a,b) (-EINVAL) +#endif +#ifndef SET_ENDIAN +# define SET_ENDIAN(a,b) (-EINVAL) +#endif /* * this is where the system-wide overflow UID and GID are defined, for @@ -132,14 +136,15 @@ static int __kprobes notifier_call_chain(struct notifier_block **nl, unsigned long val, void *v) { int ret = NOTIFY_DONE; - struct notifier_block *nb; + struct notifier_block *nb, *next_nb; nb = rcu_dereference(*nl); while (nb) { + next_nb = rcu_dereference(nb->next); ret = nb->notifier_call(nb, val, v); if ((ret & NOTIFY_STOP_MASK) == NOTIFY_STOP_MASK) break; - nb = rcu_dereference(nb->next); + nb = next_nb; } return ret; } @@ -583,7 +588,7 @@ void emergency_restart(void) } EXPORT_SYMBOL_GPL(emergency_restart); -void kernel_restart_prepare(char *cmd) +static void kernel_restart_prepare(char *cmd) { blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd); system_state = SYSTEM_RESTART; @@ -617,7 +622,7 @@ EXPORT_SYMBOL_GPL(kernel_restart); * Move into place and start executing a preloaded standalone * executable. If nothing was preloaded return an error. */ -void kernel_kexec(void) +static void kernel_kexec(void) { #ifdef CONFIG_KEXEC struct kimage *image; @@ -631,7 +636,6 @@ void kernel_kexec(void) machine_kexec(image); #endif } -EXPORT_SYMBOL_GPL(kernel_kexec); void kernel_shutdown_prepare(enum system_states state) { @@ -1860,23 +1864,20 @@ out: * fields when reaping, so a sample either gets all the additions of a * given child after it's reaped, or none so this sample is before reaping. * - * tasklist_lock locking optimisation: - * If we are current and single threaded, we do not need to take the tasklist - * lock or the siglock. No one else can take our signal_struct away, - * no one else can reap the children to update signal->c* counters, and - * no one else can race with the signal-> fields. - * If we do not take the tasklist_lock, the signal-> fields could be read - * out of order while another thread was just exiting. So we place a - * read memory barrier when we avoid the lock. On the writer side, - * write memory barrier is implied in __exit_signal as __exit_signal releases - * the siglock spinlock after updating the signal-> fields. - * - * We don't really need the siglock when we access the non c* fields - * of the signal_struct (for RUSAGE_SELF) even in multithreaded - * case, since we take the tasklist lock for read and the non c* signal-> - * fields are updated only in __exit_signal, which is called with - * tasklist_lock taken for write, hence these two threads cannot execute - * concurrently. + * Locking: + * We need to take the siglock for CHILDEREN, SELF and BOTH + * for the cases current multithreaded, non-current single threaded + * non-current multithreaded. Thread traversal is now safe with + * the siglock held. + * Strictly speaking, we donot need to take the siglock if we are current and + * single threaded, as no one else can take our signal_struct away, no one + * else can reap the children to update signal->c* counters, and no one else + * can race with the signal-> fields. If we do not take any lock, the + * signal-> fields could be read out of order while another thread was just + * exiting. So we should place a read memory barrier when we avoid the lock. + * On the writer side, write memory barrier is implied in __exit_signal + * as __exit_signal releases the siglock spinlock after updating the signal-> + * fields. But we don't do this yet to keep things simple. * */ @@ -1885,35 +1886,25 @@ static void k_getrusage(struct task_struct *p, int who, struct rusage *r) struct task_struct *t; unsigned long flags; cputime_t utime, stime; - int need_lock = 0; memset((char *) r, 0, sizeof *r); utime = stime = cputime_zero; - if (p != current || !thread_group_empty(p)) - need_lock = 1; - - if (need_lock) { - read_lock(&tasklist_lock); - if (unlikely(!p->signal)) { - read_unlock(&tasklist_lock); - return; - } - } else - /* See locking comments above */ - smp_rmb(); + rcu_read_lock(); + if (!lock_task_sighand(p, &flags)) { + rcu_read_unlock(); + return; + } switch (who) { case RUSAGE_BOTH: case RUSAGE_CHILDREN: - spin_lock_irqsave(&p->sighand->siglock, flags); utime = p->signal->cutime; stime = p->signal->cstime; r->ru_nvcsw = p->signal->cnvcsw; r->ru_nivcsw = p->signal->cnivcsw; r->ru_minflt = p->signal->cmin_flt; r->ru_majflt = p->signal->cmaj_flt; - spin_unlock_irqrestore(&p->sighand->siglock, flags); if (who == RUSAGE_CHILDREN) break; @@ -1941,8 +1932,9 @@ static void k_getrusage(struct task_struct *p, int who, struct rusage *r) BUG(); } - if (need_lock) - read_unlock(&tasklist_lock); + unlock_task_sighand(p, &flags); + rcu_read_unlock(); + cputime_to_timeval(utime, &r->ru_utime); cputime_to_timeval(stime, &r->ru_stime); } @@ -2057,6 +2049,13 @@ asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3, return -EFAULT; return 0; } + case PR_GET_ENDIAN: + error = GET_ENDIAN(current, arg2); + break; + case PR_SET_ENDIAN: + error = SET_ENDIAN(current, arg2); + break; + default: error = -EINVAL; break; |