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 */
19 cpumask_t mt_fpu_cpumask;
20
21 static int fpaff_threshold = -1;
22 unsigned 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 */
find_process_by_pid(pid_t pid)38 static 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 */
check_same_owner(struct task_struct * p)46 static 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 */
mipsmt_sys_sched_setaffinity(pid_t pid,unsigned int len,unsigned long __user * user_mask_ptr)62 asmlinkage 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 cpus_intersects(*new_mask, mt_fpu_cpumask)) {
118 cpus_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 }
138 out_unlock:
139 free_cpumask_var(effective_mask);
140 out_free_new_mask:
141 free_cpumask_var(new_mask);
142 out_free_cpus_allowed:
143 free_cpumask_var(cpus_allowed);
144 out_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 */
mipsmt_sys_sched_getaffinity(pid_t pid,unsigned int len,unsigned long __user * user_mask_ptr)153 asmlinkage 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
179 out_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
fpaff_thresh(char * str)190 static 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
mt_fp_affinity_init(void)202 static __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 }
215 arch_initcall(mt_fp_affinity_init);
216