1/*
2 * General MIPS MT support routines, usable in AP/SP and SMVP.
3 * Copyright (C) 2005 Mips Technologies, Inc
4 */
5#include <linux/cpu.h>
6#include <linux/cpuset.h>
7#include <linux/cpumask.h>
8#include <linux/delay.h>
9#include <linux/kernel.h>
10#include <linux/init.h>
11#include <linux/sched.h>
12#include <linux/security.h>
13#include <linux/types.h>
14#include <asm/uaccess.h>
15
16/*
17 * CPU mask used to set process affinity for MT VPEs/TCs with FPUs
18 */
19cpumask_t mt_fpu_cpumask;
20
21static int fpaff_threshold = -1;
22unsigned long mt_fpemul_threshold;
23
24/*
25 * Replacement functions for the sys_sched_setaffinity() and
26 * sys_sched_getaffinity() system calls, so that we can integrate
27 * FPU affinity with the user's requested processor affinity.
28 * This code is 98% identical with the sys_sched_setaffinity()
29 * and sys_sched_getaffinity() system calls, and should be
30 * updated when kernel/sched/core.c changes.
31 */
32
33/*
34 * find_process_by_pid - find a process with a matching PID value.
35 * used in sys_sched_set/getaffinity() in kernel/sched/core.c, so
36 * cloned here.
37 */
38static inline struct task_struct *find_process_by_pid(pid_t pid)
39{
40	return pid ? find_task_by_vpid(pid) : current;
41}
42
43/*
44 * check the target process has a UID that matches the current process's
45 */
46static bool check_same_owner(struct task_struct *p)
47{
48	const struct cred *cred = current_cred(), *pcred;
49	bool match;
50
51	rcu_read_lock();
52	pcred = __task_cred(p);
53	match = (uid_eq(cred->euid, pcred->euid) ||
54		 uid_eq(cred->euid, pcred->uid));
55	rcu_read_unlock();
56	return match;
57}
58
59/*
60 * mipsmt_sys_sched_setaffinity - set the cpu affinity of a process
61 */
62asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len,
63				      unsigned long __user *user_mask_ptr)
64{
65	cpumask_var_t cpus_allowed, new_mask, effective_mask;
66	struct thread_info *ti;
67	struct task_struct *p;
68	int retval;
69
70	if (len < sizeof(new_mask))
71		return -EINVAL;
72
73	if (copy_from_user(&new_mask, user_mask_ptr, sizeof(new_mask)))
74		return -EFAULT;
75
76	get_online_cpus();
77	rcu_read_lock();
78
79	p = find_process_by_pid(pid);
80	if (!p) {
81		rcu_read_unlock();
82		put_online_cpus();
83		return -ESRCH;
84	}
85
86	/* Prevent p going away */
87	get_task_struct(p);
88	rcu_read_unlock();
89
90	if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
91		retval = -ENOMEM;
92		goto out_put_task;
93	}
94	if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
95		retval = -ENOMEM;
96		goto out_free_cpus_allowed;
97	}
98	if (!alloc_cpumask_var(&effective_mask, GFP_KERNEL)) {
99		retval = -ENOMEM;
100		goto out_free_new_mask;
101	}
102	retval = -EPERM;
103	if (!check_same_owner(p) && !capable(CAP_SYS_NICE))
104		goto out_unlock;
105
106	retval = security_task_setscheduler(p);
107	if (retval)
108		goto out_unlock;
109
110	/* Record new user-specified CPU set for future reference */
111	cpumask_copy(&p->thread.user_cpus_allowed, new_mask);
112
113 again:
114	/* Compute new global allowed CPU set if necessary */
115	ti = task_thread_info(p);
116	if (test_ti_thread_flag(ti, TIF_FPUBOUND) &&
117	    cpumask_intersects(new_mask, &mt_fpu_cpumask)) {
118		cpumask_and(effective_mask, new_mask, &mt_fpu_cpumask);
119		retval = set_cpus_allowed_ptr(p, effective_mask);
120	} else {
121		cpumask_copy(effective_mask, new_mask);
122		clear_ti_thread_flag(ti, TIF_FPUBOUND);
123		retval = set_cpus_allowed_ptr(p, new_mask);
124	}
125
126	if (!retval) {
127		cpuset_cpus_allowed(p, cpus_allowed);
128		if (!cpumask_subset(effective_mask, cpus_allowed)) {
129			/*
130			 * We must have raced with a concurrent cpuset
131			 * update. Just reset the cpus_allowed to the
132			 * cpuset's cpus_allowed
133			 */
134			cpumask_copy(new_mask, cpus_allowed);
135			goto again;
136		}
137	}
138out_unlock:
139	free_cpumask_var(effective_mask);
140out_free_new_mask:
141	free_cpumask_var(new_mask);
142out_free_cpus_allowed:
143	free_cpumask_var(cpus_allowed);
144out_put_task:
145	put_task_struct(p);
146	put_online_cpus();
147	return retval;
148}
149
150/*
151 * mipsmt_sys_sched_getaffinity - get the cpu affinity of a process
152 */
153asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
154				      unsigned long __user *user_mask_ptr)
155{
156	unsigned int real_len;
157	cpumask_t allowed, mask;
158	int retval;
159	struct task_struct *p;
160
161	real_len = sizeof(mask);
162	if (len < real_len)
163		return -EINVAL;
164
165	get_online_cpus();
166	read_lock(&tasklist_lock);
167
168	retval = -ESRCH;
169	p = find_process_by_pid(pid);
170	if (!p)
171		goto out_unlock;
172	retval = security_task_getscheduler(p);
173	if (retval)
174		goto out_unlock;
175
176	cpumask_or(&allowed, &p->thread.user_cpus_allowed, &p->cpus_allowed);
177	cpumask_and(&mask, &allowed, cpu_active_mask);
178
179out_unlock:
180	read_unlock(&tasklist_lock);
181	put_online_cpus();
182	if (retval)
183		return retval;
184	if (copy_to_user(user_mask_ptr, &mask, real_len))
185		return -EFAULT;
186	return real_len;
187}
188
189
190static int __init fpaff_thresh(char *str)
191{
192	get_option(&str, &fpaff_threshold);
193	return 1;
194}
195__setup("fpaff=", fpaff_thresh);
196
197/*
198 * FPU Use Factor empirically derived from experiments on 34K
199 */
200#define FPUSEFACTOR 2000
201
202static __init int mt_fp_affinity_init(void)
203{
204	if (fpaff_threshold >= 0) {
205		mt_fpemul_threshold = fpaff_threshold;
206	} else {
207		mt_fpemul_threshold =
208			(FPUSEFACTOR * (loops_per_jiffy/(500000/HZ))) / HZ;
209	}
210	printk(KERN_DEBUG "FPU Affinity set after %ld emulations\n",
211	       mt_fpemul_threshold);
212
213	return 0;
214}
215arch_initcall(mt_fp_affinity_init);
216