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Subject[PATCH] syscall interface for cpu affinity
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Linus,

I have updated the patch a bit and resycned to 2.5.6. Are you
interested? I believe a user interface for setting task CPU affinity is
useful and completes the rest of our sched_* syscalls. A syscall
implementation seems to be what everyone wants (I have a proc-interface,
too...)

This patch implements

int sched_set_affinity(pid_t pid, unsigned int len,
unsigned long *new_mask_ptr);

int sched_get_affinity(pid_t pid, unsigned int *user_len_ptr,
unsigned long *user_mask_ptr)

which set and get the cpu affinity (task->cpus_allowed) for a task,
using the set_cpus_allowed function in Ingo's scheduler. The functions
properly support changes to cpus_allowed, implement security, and are
well-tested.

They are based on Ingo's older affinity syscall patch and my older
affinity proc patch.

Comments?

Robert Love

diff -urN linux-2.5.6/arch/i386/kernel/entry.S linux/arch/i386/kernel/entry.S
--- linux-2.5.6/arch/i386/kernel/entry.S Thu Mar 7 21:18:19 2002
+++ linux/arch/i386/kernel/entry.S Sun Mar 10 13:01:03 2002
@@ -717,6 +717,8 @@
.long SYMBOL_NAME(sys_fremovexattr)
.long SYMBOL_NAME(sys_tkill)
.long SYMBOL_NAME(sys_sendfile64)
+ .long SYMBOL_NAME(sys_sched_set_affinity) /* 240 */
+ .long SYMBOL_NAME(sys_sched_get_affinity)

.rept NR_syscalls-(.-sys_call_table)/4
.long SYMBOL_NAME(sys_ni_syscall)
diff -urN linux-2.5.6/include/asm-i386/unistd.h linux/include/asm-i386/unistd.h
--- linux-2.5.6/include/asm-i386/unistd.h Thu Mar 7 21:18:55 2002
+++ linux/include/asm-i386/unistd.h Sun Mar 10 13:03:41 2002
@@ -244,6 +244,8 @@
#define __NR_fremovexattr 237
#define __NR_tkill 238
#define __NR_sendfile64 239
+#define __NR_sched_set_affinity 240
+#define __NR_sched_get_affinity 241

/* user-visible error numbers are in the range -1 - -124: see <asm-i386/errno.h> */

diff -urN linux-2.5.6/kernel/sched.c linux/kernel/sched.c
--- linux-2.5.6/kernel/sched.c Thu Mar 7 21:18:19 2002
+++ linux/kernel/sched.c Sun Mar 10 12:59:26 2002
@@ -1215,6 +1215,95 @@
return retval;
}

+/**
+ * sys_sched_set_affinity - set the cpu affinity of a process
+ * @pid: pid of the process
+ * @len: length of new_mask
+ * @new_mask: user-space pointer to the new cpu mask
+ */
+asmlinkage int sys_sched_set_affinity(pid_t pid, unsigned int len,
+ unsigned long *new_mask_ptr)
+{
+ unsigned long new_mask;
+ task_t *p;
+ int retval;
+
+ if (len < sizeof(new_mask))
+ return -EINVAL;
+
+ if (copy_from_user(&new_mask, new_mask_ptr, sizeof(new_mask)))
+ return -EFAULT;
+
+ new_mask &= cpu_online_map;
+ if (!new_mask)
+ return -EINVAL;
+
+ read_lock(&tasklist_lock);
+
+ retval = -ESRCH;
+ p = find_process_by_pid(pid);
+ if (!p)
+ goto out_unlock;
+
+ retval = -EPERM;
+ if ((current->euid != p->euid) && (current->euid != p->uid) &&
+ !capable(CAP_SYS_NICE))
+ goto out_unlock;
+
+ retval = 0;
+#ifdef CONFIG_SMP
+ set_cpus_allowed(p, new_mask);
+#endif
+
+out_unlock:
+ read_unlock(&tasklist_lock);
+ return retval;
+}
+
+/**
+ * sys_sched_get_affinity - get the cpu affinity of a process
+ * @pid: pid of the process
+ * @user_len_ptr: userspace pointer to the length of the mask
+ * @user_mask_ptr: userspace pointer to the mask
+ */
+asmlinkage int sys_sched_get_affinity(pid_t pid, unsigned int *user_len_ptr,
+ unsigned long *user_mask_ptr)
+{
+ unsigned long mask;
+ unsigned int len, user_len;
+ task_t *p;
+ int retval;
+
+ len = sizeof(mask);
+
+ if (copy_from_user(&user_len, user_len_ptr, sizeof(user_len)))
+ return -EFAULT;
+
+ if (copy_to_user(user_len_ptr, &len, sizeof(len)))
+ return -EFAULT;
+
+ if (user_len < len)
+ return -EINVAL;
+
+ read_lock(&tasklist_lock);
+
+ retval = -ESRCH;
+ p = find_process_by_pid(pid);
+ if (!p)
+ goto out_unlock;
+
+ retval = 0;
+ mask = p->cpus_allowed & cpu_online_map;
+
+out_unlock:
+ read_unlock(&tasklist_lock);
+ if (retval)
+ return retval;
+ if (copy_to_user(user_mask_ptr, &mask, sizeof(mask)))
+ return -EFAULT;
+ return 0;
+}
+
asmlinkage long sys_sched_yield(void)
{
runqueue_t *rq;
-
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