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Linux/arch/mips/kernel/mips-mt-fpaff.c

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  1 /*
  2  * General MIPS MT support routines, usable in AP/SP, SMVP, or SMTC kernels
  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  */
 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  */
 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  */
 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  */
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 
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 
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 

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