From 651d765d0b2c72d33430487c8b6ef64c60cd2134 Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Wed, 7 Jun 2006 16:10:19 +1000 Subject: [PATCH] Add a prctl to change the endianness of a process. This new prctl is intended for changing the execution mode of the processor, on processors that support both a little-endian mode and a big-endian mode. It is intended for use by programs such as instruction set emulators (for example an x86 emulator on PowerPC), which may find it convenient to use the processor in an alternate endianness mode when executing translated instructions. Note that this does not imply the existence of a fully-fledged ABI for both endiannesses, or of compatibility code for converting system calls done in the non-native endianness mode. The program is expected to arrange for all of its system call arguments to be presented in the native endianness. Switching between big and little-endian mode will require some care in constructing the instruction sequence for the switch. Generally the instructions up to the instruction that invokes the prctl system call will have to be in the old endianness, and subsequent instructions will have to be in the new endianness. Signed-off-by: Anton Blanchard Signed-off-by: Paul Mackerras --- kernel/sys.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'kernel/sys.c') diff --git a/kernel/sys.c b/kernel/sys.c index 0b6ec0e7936..12d2d753dc3 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -57,6 +57,12 @@ #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 @@ -2057,6 +2063,13 @@ 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; -- cgit v1.2.3-70-g09d2 From de047c1bcd7f7bcfbdc29eb5b439fb332594da3f Mon Sep 17 00:00:00 2001 From: Ravikiran G Thirumalai Date: Thu, 22 Jun 2006 14:47:26 -0700 Subject: [PATCH] avoid tasklist_lock at getrusage for multithreaded case too Avoid taking tasklist_lock for at getrusage for the multithreaded case too. We don't need to take the tasklist lock for thread traversal of a process since Oleg's do-__unhash_process-under-siglock.patch and related work. Signed-off-by: Ravikiran Thirumalai Cc: Oleg Nesterov Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/sys.c | 56 ++++++++++++++++++++++---------------------------------- 1 file changed, 22 insertions(+), 34 deletions(-) (limited to 'kernel/sys.c') diff --git a/kernel/sys.c b/kernel/sys.c index 0b6ec0e7936..fc9ebbbaba0 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1860,23 +1860,20 @@ 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 +1882,25 @@ 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 +1928,9 @@ 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); } -- cgit v1.2.3-70-g09d2 From 55f4e8d156d23709739029afb108932ef94cac94 Mon Sep 17 00:00:00 2001 From: Jes Sorensen Date: Fri, 23 Jun 2006 02:05:50 -0700 Subject: [PATCH] kernel/sys.c doesn't need init.h kernel/sys.c doesn't have anything in it relying on linux/init.h - remove the include. Signed-off-by: Jes Sorensen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/sys.c | 1 - 1 file changed, 1 deletion(-) (limited to 'kernel/sys.c') diff --git a/kernel/sys.c b/kernel/sys.c index a57a00597ce..90930b28d2c 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -13,7 +13,6 @@ #include #include #include -#include #include #include #include -- cgit v1.2.3-70-g09d2