On Sun, 17 Nov 2002, Linus Torvalds wrote:
> I'm convinced. However, I still want som elargely cosmetic changes to the
> patch, Ingo:
>
> - the existing CLONE_SETTID should be called CLONE_PARENT_SETTID, because
> that is how it already works since it is done after the VM copy (this
> is what your patch already does)
> - the existing CLONE_CLEARTID should then be CLONE_CHILD_CLEARTID (your
> existing patch re-numbers this) and using existing semantics
> - the new flag should be CLONE_CHILD_SETTID, and should _not_ renumber
> old existing bits (your existing patch renumbers everything, including
> totally unrelated bits like CLONE_DETATCHED)
ok, done.
> - please don't introduce a new pointer, just use the old one. There
> appears to be no cases where you want to have different pointers
> anyway.
i'm against this simplification, as it makes CLONE_CHILD_SETTID and
CLONE_PARENT_SETTID mutually exclusive. Ulrich does not use the two flags
at once currently, but there's no reason to restrict the API to match the
current usage pattern. This enables a safer fork() variant that guarantees
the setting of the child PID before starting the new context.
i've attached my current patch against BK-curr, which also solves the
problem Ulrich mentioned - it splits up ->user_tid into ->set_child_tid
and ->clear_child_tid pointers. This way the clearing and setting
functionality is cleanly separated.
(plus the new syscall # is now in unistd.h)
Ingo
--- linux/arch/i386/kernel/entry.S.orig 2002-11-17 20:54:55.000000000 +0100
+++ linux/arch/i386/kernel/entry.S 2002-11-17 20:57:44.000000000 +0100
@@ -193,10 +193,8 @@
ENTRY(ret_from_fork)
-#if CONFIG_SMP || CONFIG_PREEMPT
# NOTE: this function takes a parameter but it's unused on x86.
call schedule_tail
-#endif
GET_THREAD_INFO(%ebx)
jmp syscall_exit
--- linux/arch/i386/kernel/smpboot.c.orig 2002-11-17 21:12:49.000000000 +0100
+++ linux/arch/i386/kernel/smpboot.c 2002-11-17 21:12:52.000000000 +0100
@@ -498,7 +498,7 @@
* don't care about the eip and regs settings since
* we'll never reschedule the forked task.
*/
- return do_fork(CLONE_VM|CLONE_IDLETASK, 0, ®s, 0, NULL);
+ return do_fork(CLONE_VM|CLONE_IDLETASK, 0, ®s, 0, NULL, NULL);
}
/* which physical APIC ID maps to which logical CPU number */
--- linux/arch/i386/kernel/process.c.orig 2002-11-17 21:03:01.000000000 +0100
+++ linux/arch/i386/kernel/process.c 2002-11-18 10:04:56.000000000 +0100
@@ -225,7 +225,7 @@
regs.eflags = 0x286;
/* Ok, create the new process.. */
- p = do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, ®s, 0, NULL);
+ p = do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, ®s, 0, NULL, NULL);
return IS_ERR(p) ? PTR_ERR(p) : p->pid;
}
@@ -287,7 +287,7 @@
struct_cpy(childregs, regs);
childregs->eax = 0;
childregs->esp = esp;
- p->user_tid = NULL;
+ p->set_child_tid = p->clear_child_tid = NULL;
p->thread.esp = (unsigned long) childregs;
p->thread.esp0 = (unsigned long) (childregs+1);
@@ -502,7 +502,7 @@
{
struct task_struct *p;
- p = do_fork(SIGCHLD, regs.esp, ®s, 0, NULL);
+ p = do_fork(SIGCHLD, regs.esp, ®s, 0, NULL, NULL);
return IS_ERR(p) ? PTR_ERR(p) : p->pid;
}
@@ -511,14 +511,15 @@
struct task_struct *p;
unsigned long clone_flags;
unsigned long newsp;
- int *user_tid;
+ int *parent_tidptr, *child_tidptr;
clone_flags = regs.ebx;
newsp = regs.ecx;
- user_tid = (int *)regs.edx;
+ parent_tidptr = (int *)regs.edx;
+ child_tidptr = (int *)regs.esi;
if (!newsp)
newsp = regs.esp;
- p = do_fork(clone_flags & ~CLONE_IDLETASK, newsp, ®s, 0, user_tid);
+ p = do_fork(clone_flags & ~CLONE_IDLETASK, newsp, ®s, 0, parent_tidptr, child_tidptr);
return IS_ERR(p) ? PTR_ERR(p) : p->pid;
}
@@ -536,7 +537,7 @@
{
struct task_struct *p;
- p = do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs.esp, ®s, 0, NULL);
+ p = do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs.esp, ®s, 0, NULL, NULL);
return IS_ERR(p) ? PTR_ERR(p) : p->pid;
}
--- linux/include/linux/sched.h.orig 2002-11-17 20:53:52.000000000 +0100
+++ linux/include/linux/sched.h 2002-11-18 10:04:09.000000000 +0100
@@ -46,10 +46,11 @@
#define CLONE_NEWNS 0x00020000 /* New namespace group? */
#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_CLEARTID 0x00200000 /* clear the userspace TID */
-#define CLONE_DETACHED 0x00400000 /* parent wants no child-exit signal */
-#define CLONE_UNTRACED 0x00800000 /* set if the tracing process can't force CLONE_PTRACE on this clone */
+#define CLONE_PARENT_SETTID 0x00100000 /* set the TID in the parent */
+#define CLONE_CHILD_CLEARTID 0x00200000 /* clear the TID in the child */
+#define CLONE_DETACHED 0x00400000 /* parent wants no child-exit signal */
+#define CLONE_UNTRACED 0x00800000 /* set if the tracing process can't force CLONE_PTRACE on this clone */
+#define CLONE_CHILD_SETTID 0x01000000 /* set the TID in the child */
/*
* List of flags we want to share for kernel threads,
@@ -332,7 +333,8 @@
wait_queue_head_t wait_chldexit; /* for wait4() */
struct completion *vfork_done; /* for vfork() */
- int *user_tid; /* for CLONE_CLEARTID */
+ int *set_child_tid; /* CLONE_CHILD_SETTID */
+ int *clear_child_tid; /* CLONE_CHILD_CLEARTID */
unsigned long rt_priority;
unsigned long it_real_value, it_prof_value, it_virt_value;
@@ -615,7 +617,7 @@
extern task_t *child_reaper;
extern int do_execve(char *, char **, char **, struct pt_regs *);
-extern struct task_struct *do_fork(unsigned long, unsigned long, struct pt_regs *, unsigned long, int *);
+extern struct task_struct *do_fork(unsigned long, unsigned long, struct pt_regs *, unsigned long, int *, int *);
#ifdef CONFIG_SMP
extern void wait_task_inactive(task_t * p);
--- linux/include/asm-i386/unistd.h.orig 2002-11-18 10:06:42.000000000 +0100
+++ linux/include/asm-i386/unistd.h 2002-11-18 10:07:00.000000000 +0100
@@ -262,6 +262,7 @@
#define __NR_sys_epoll_ctl 255
#define __NR_sys_epoll_wait 256
#define __NR_remap_file_pages 257
+#define __NR_set_tid_address 258
/* user-visible error numbers are in the range -1 - -124: see <asm-i386/errno.h> */
--- linux/kernel/sched.c.orig 2002-11-17 20:52:30.000000000 +0100
+++ linux/kernel/sched.c 2002-11-18 10:05:30.000000000 +0100
@@ -503,12 +503,16 @@
* schedule_tail - first thing a freshly forked thread must call.
* @prev: the thread we just switched away from.
*/
-#if CONFIG_SMP || CONFIG_PREEMPT
+asmlinkage void FASTCALL(schedule_tail(task_t *prev));
asmlinkage void schedule_tail(task_t *prev)
{
finish_arch_switch(this_rq(), prev);
+ /*
+ * Does the child thread/process want to be notified of the TID/PID?
+ */
+ if (current->set_child_tid)
+ put_user(current->pid, current->set_child_tid);
}
-#endif
/*
* context_switch - switch to the new MM and the new
--- linux/kernel/fork.c.orig 2002-11-17 20:54:55.000000000 +0100
+++ linux/kernel/fork.c 2002-11-18 10:08:15.000000000 +0100
@@ -407,13 +407,13 @@
tsk->vfork_done = NULL;
complete(vfork_done);
}
- if (tsk->user_tid) {
+ if (tsk->clear_child_tid) {
/*
* We dont check the error code - if userspace has
* not set up a proper pointer then tough luck.
*/
- put_user(0, tsk->user_tid);
- sys_futex((unsigned long)tsk->user_tid, FUTEX_WAKE, 1, NULL);
+ put_user(0, tsk->clear_child_tid);
+ sys_futex((unsigned long)tsk->clear_child_tid, FUTEX_WAKE, 1, NULL);
}
}
@@ -676,9 +676,9 @@
p->flags = new_flags;
}
-asmlinkage int sys_set_tid_address(int *user_tid)
+asmlinkage int sys_set_tid_address(int *tidptr)
{
- current->user_tid = user_tid;
+ current->clear_child_tid = tidptr;
return current->pid;
}
@@ -695,7 +695,8 @@
unsigned long stack_start,
struct pt_regs *regs,
unsigned long stack_size,
- int *user_tid)
+ int *parent_tidptr,
+ int *child_tidptr)
{
int retval;
struct task_struct *p = NULL;
@@ -819,19 +820,20 @@
retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
if (retval)
goto bad_fork_cleanup_namespace;
- /*
- * Notify the child of the TID?
- */
- retval = -EFAULT;
- if (clone_flags & CLONE_SETTID)
- if (put_user(p->pid, user_tid))
- goto bad_fork_cleanup_namespace;
+ if (clone_flags & CLONE_PARENT_SETTID)
+ if (put_user(p->pid, parent_tidptr)) {
+ retval = -EFAULT;
+ goto bad_fork_cleanup_namespace;
+ }
/*
- * Does the userspace VM want the TID cleared on mm_release()?
+ * Does the userspace VM want the TID set in the child's
+ * address space? And/or get it cleared on mm_release()?
*/
- if (clone_flags & CLONE_CLEARTID)
- p->user_tid = user_tid;
+ if (clone_flags & CLONE_CHILD_SETTID)
+ p->set_child_tid = child_tidptr;
+ if (clone_flags & CLONE_CHILD_CLEARTID)
+ p->clear_child_tid = child_tidptr;
/*
* Syscall tracing should be turned off in the child regardless
@@ -1000,7 +1002,8 @@
unsigned long stack_start,
struct pt_regs *regs,
unsigned long stack_size,
- int *user_tid)
+ int *parent_tidptr,
+ int *child_tidptr)
{
struct task_struct *p;
int trace = 0;
@@ -1011,7 +1014,7 @@
clone_flags |= CLONE_PTRACE;
}
- p = copy_process(clone_flags, stack_start, regs, stack_size, user_tid);
+ p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr);
if (!IS_ERR(p)) {
struct completion vfork;
-
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This archive was generated by hypermail 2b29 : Sat Nov 23 2002 - 22:00:21 EST