the attached patch implements CLONE_VM_RELEASE, which lets the child
release the 'user VM' at mm_release() time.
note that a quick testing did not show the desired result yet, so there
must be some thinko in it, but this is how i think it would roughly look
like. The copy_thread() code takes a pointer away from the user-stack -
userspace should put the lock there.
the patch also accelerates the common 'no funky CLONE flags' case in
copy_thread(), since the flags started mounting up.
(the patch is ontop the SETTID/SETTLS and DETACHED patches, for dependency
reasons.)
Ingo
--- linux/arch/i386/kernel/process.c.orig Tue Aug 13 22:26:39 2002
+++ linux/arch/i386/kernel/process.c Tue Aug 13 22:35:45 2002
@@ -566,6 +566,7 @@
struct_cpy(childregs, regs);
childregs->eax = 0;
childregs->esp = esp;
+ p->user_vm_lock = NULL;
p->thread.esp = (unsigned long) childregs;
p->thread.esp0 = (unsigned long) (childregs+1);
@@ -579,6 +580,19 @@
unlazy_fpu(tsk);
struct_cpy(&p->thread.i387, &tsk->thread.i387);
+ if (unlikely(NULL != tsk->thread.ts_io_bitmap)) {
+ p->thread.ts_io_bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
+ if (!p->thread.ts_io_bitmap)
+ return -ENOMEM;
+ memcpy(p->thread.ts_io_bitmap, tsk->thread.ts_io_bitmap,
+ IO_BITMAP_BYTES);
+ }
+
+ /*
+ * The common fastpath:
+ */
+ if (!(clone_flags & (CLONE_SETTLS | CLONE_SETTID | CLONE_RELEASE_VM)))
+ return 0;
/*
* Set a new TLS for the child thread?
*/
@@ -608,14 +622,13 @@
if (put_user(p->pid, (pid_t *)childregs->edx))
return -EFAULT;
- if (unlikely(NULL != tsk->thread.ts_io_bitmap)) {
- p->thread.ts_io_bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
- if (!p->thread.ts_io_bitmap)
- return -ENOMEM;
- memcpy(p->thread.ts_io_bitmap, tsk->thread.ts_io_bitmap,
- IO_BITMAP_BYTES);
+ /*
+ * Does the userspace VM want any unlock on mm_release()?
+ */
+ if (clone_flags & CLONE_RELEASE_VM) {
+ childregs->esp -= sizeof(0UL);
+ p->user_vm_lock = (long *) esp;
}
-
return 0;
}
--- linux/include/linux/sched.h.orig Tue Aug 13 22:20:41 2002
+++ linux/include/linux/sched.h Tue Aug 13 22:35:20 2002
@@ -47,6 +47,7 @@
#define CLONE_SYSVSEM 0x00040000 /* share system V SEM_UNDO semantics */
#define CLONE_SETTLS 0x00080000 /* create a new TLS for the child */
#define CLONE_SETTID 0x00100000 /* write the TID back to userspace */
+#define CLONE_RELEASE_VM 0x00200000 /* release the userspace stack */
#define CLONE_SIGNAL (CLONE_SIGHAND | CLONE_THREAD)
@@ -305,6 +306,7 @@
wait_queue_head_t wait_chldexit; /* for wait4() */
struct completion *vfork_done; /* for vfork() */
+ long *user_vm_lock; /* for CLONE_RELEASE_VM */
unsigned long rt_priority;
unsigned long it_real_value, it_prof_value, it_virt_value;
--- linux/kernel/fork.c.orig Tue Aug 13 22:21:52 2002
+++ linux/kernel/fork.c Tue Aug 13 22:35:27 2002
@@ -367,6 +367,12 @@
tsk->vfork_done = NULL;
complete(vfork_done);
}
+ if (tsk->user_vm_lock)
+ /*
+ * We dont check the error code - if userspace has
+ * not set up a proper pointer then tough luck.
+ */
+ put_user(0UL, tsk->user_vm_lock);
}
static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
-
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This archive was generated by hypermail 2b29 : Thu Aug 15 2002 - 22:00:33 EST