From: Robert Love <rml@tech9.net>
To: linux-kernel@vger.kernel.org
Subject: [PATCH] 2.4-ac: task CPU affinity syscalls
Date: 15 May 2002 15:49:15 -0700 [thread overview]
Message-ID: <1021502955.825.23.camel@sinai> (raw)
[-- Attachment #1: Type: text/plain, Size: 1110 bytes --]
The following patch, against 2.4.19-pre8-ac4, implements the task CPU
affinity syscalls found in 2.5. This is not suggested for inclusion in
2.4 until the 2.5 interface is assuredly what we want. I post it now
for discussion and those who are interested.
The syscalls are:
sched_getaffinity(pid_t pid, unsigned long len, unsigned long *mask)
sched_setaffinity(pid_t pid, unsigned long len, unsigned long *mask)
which get and set the affinity of any given task (provided proper
permission) to the given CPU bitmask.
I believe we solved the locking issue I presented before: handle it as
in 2.5. Acquire tasklist_lock, translate the pid into a valid
task_struct, call get_task_struct to bump the task_struct's page
reference count, drop tasklist_lock, call set_cpus_allowed, then call
free_task_struct which does free_pages. Since the pages usage count was
bumped, it will not be freed unless the task prematurely deallocated in
the middle.
Comments? Hopefully this works and - assuming the 2.5 interface stays
as is - I can put this aside until it is time to merge it.
Robert Love
[-- Attachment #2: cpu-affinity-syscall-rml-2.4.19-pre8-ac4-1.patch --]
[-- Type: text/x-patch, Size: 5013 bytes --]
diff -urN linux-2.4.19-pre8-ac4/arch/i386/kernel/entry.S linux/arch/i386/kernel/entry.S
--- linux-2.4.19-pre8-ac4/arch/i386/kernel/entry.S Wed May 15 12:53:43 2002
+++ linux/arch/i386/kernel/entry.S Wed May 15 14:51:39 2002
@@ -639,8 +639,8 @@
.long SYMBOL_NAME(sys_tkill)
.long SYMBOL_NAME(sys_ni_syscall) /* reserved for sendfile64 */
.long SYMBOL_NAME(sys_ni_syscall) /* 240 reserved for futex */
- .long SYMBOL_NAME(sys_ni_syscall) /* reserved for sched_setaffinity */
- .long SYMBOL_NAME(sys_ni_syscall) /* reserved for sched_getaffinity */
+ .long SYMBOL_NAME(sys_sched_setaffinity)
+ .long SYMBOL_NAME(sys_sched_getaffinity)
.rept NR_syscalls-(.-sys_call_table)/4
.long SYMBOL_NAME(sys_ni_syscall)
diff -urN linux-2.4.19-pre8-ac4/arch/ppc/kernel/misc.S linux/arch/ppc/kernel/misc.S
--- linux-2.4.19-pre8-ac4/arch/ppc/kernel/misc.S Wed May 15 12:53:46 2002
+++ linux/arch/ppc/kernel/misc.S Wed May 15 14:53:17 2002
@@ -1162,6 +1162,22 @@
.long sys_mincore
.long sys_gettid
.long sys_tkill
+ .long sys_ni_syscall
+ .long sys_ni_syscall /* 210 */
+ .long sys_ni_syscall
+ .long sys_ni_syscall
+ .long sys_ni_syscall
+ .long sys_ni_syscall
+ .long sys_ni_syscall /* 215 */
+ .long sys_ni_syscall
+ .long sys_ni_syscall
+ .long sys_ni_syscall
+ .long sys_ni_syscall
+ .long sys_ni_syscall /* 220 */
+ .long sys_ni_syscall
+ .long sys_sched_setaffinity
+ .long sys_sched_getaffinity
+
.rept NR_syscalls-(.-sys_call_table)/4
.long sys_ni_syscall
.endr
diff -urN linux-2.4.19-pre8-ac4/include/asm-ppc/unistd.h linux/include/asm-ppc/unistd.h
--- linux-2.4.19-pre8-ac4/include/asm-ppc/unistd.h Wed May 15 12:53:42 2002
+++ linux/include/asm-ppc/unistd.h Wed May 15 14:53:00 2002
@@ -216,6 +216,8 @@
#define __NR_mincore 206
#define __NR_gettid 207
#define __NR_tkill 208
+#define __NR_sched_setaffinity 222
+#define __NR_sched_getaffinity 223
#define __NR(n) #n
diff -urN linux-2.4.19-pre8-ac4/include/linux/capability.h linux/include/linux/capability.h
--- linux-2.4.19-pre8-ac4/include/linux/capability.h Wed May 15 12:53:42 2002
+++ linux/include/linux/capability.h Wed May 15 14:51:39 2002
@@ -243,6 +243,7 @@
/* Allow use of FIFO and round-robin (realtime) scheduling on own
processes and setting the scheduling algorithm used by another
process. */
+/* Allow setting cpu affinity on other processes */
#define CAP_SYS_NICE 23
diff -urN linux-2.4.19-pre8-ac4/kernel/sched.c linux/kernel/sched.c
--- linux-2.4.19-pre8-ac4/kernel/sched.c Wed May 15 12:53:42 2002
+++ linux/kernel/sched.c Wed May 15 14:56:04 2002
@@ -1187,6 +1187,98 @@
return retval;
}
+/**
+ * sys_sched_setaffinity - set the cpu affinity of a process
+ * @pid: pid of the process
+ * @len: length in bytes of the bitmask pointed to by user_mask_ptr
+ * @user_mask_ptr: user-space pointer to the new cpu mask
+ */
+asmlinkage int sys_sched_setaffinity(pid_t pid, unsigned int len,
+ unsigned long *user_mask_ptr)
+{
+ unsigned long new_mask;
+ task_t *p;
+ int retval;
+
+ if (len < sizeof(new_mask))
+ return -EINVAL;
+
+ if (copy_from_user(&new_mask, user_mask_ptr, sizeof(new_mask)))
+ return -EFAULT;
+
+ new_mask &= cpu_online_map;
+ if (!new_mask)
+ return -EINVAL;
+
+ /*
+ * We cannot hold a lock across a call to set_cpus_allowed, however
+ * we need to assure our task does not slip out from under us. Since
+ * we are only concerned that its task_struct remains, we can pin it
+ * here and decrement the usage count when we are done.
+ */
+ read_lock(&tasklist_lock);
+
+ retval = -ESRCH;
+ p = find_process_by_pid(pid);
+ if (!p) {
+ read_unlock(&tasklist_lock);
+ goto out_unlock;
+ }
+
+ get_task_struct(p);
+ read_unlock(&tasklist_lock);
+
+ retval = -EPERM;
+ if ((current->euid != p->euid) && (current->euid != p->uid) &&
+ !capable(CAP_SYS_NICE))
+ goto out_unlock;
+
+ retval = 0;
+ set_cpus_allowed(p, new_mask);
+
+out_unlock:
+ free_task_struct(p);
+ return retval;
+}
+
+/**
+ * sys_sched_getaffinity - get the cpu affinity of a process
+ * @pid: pid of the process
+ * @len: length in bytes of the bitmask pointed to by user_mask_ptr
+ * @user_mask_ptr: user-space pointer to hold the current cpu mask
+ */
+asmlinkage int sys_sched_getaffinity(pid_t pid, unsigned int len,
+ unsigned long *user_mask_ptr)
+{
+ unsigned long mask;
+ unsigned int real_len;
+ task_t *p;
+ int retval;
+
+ real_len = sizeof(mask);
+
+ if (len < real_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, real_len))
+ return -EFAULT;
+ return real_len;
+}
+
asmlinkage long sys_sched_yield(void)
{
runqueue_t *rq;
reply other threads:[~2002-05-15 22:49 UTC|newest]
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