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Commit 54d8d3b5 authored by Paolo 'Blaisorblade' Giarrusso's avatar Paolo 'Blaisorblade' Giarrusso Committed by Linus Torvalds
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[PATCH] uml: add arch_switch_to for newly forked thread 



Newly forked threads have no arch_switch_to_skas() called before their first
run, because when schedule() switches to them they're resumed in the body of
thread_wait() inside fork_handler() rather than in switch_threads() in
switch_to_skas().  Compensate this missing call.

Signed-off-by: default avatarPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Acked-by: default avatarJeff Dike <jdike@addtoit.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent dd77aec0

arch/um/kernel/skas/process_kern.c

+7 −0
Original line number Diff line number Diff line
@@ -91,10 +91,17 @@ void fork_handler(int sig) 
		panic("blech");



	schedule_tail(current->thread.prev_sched);



	/* XXX: if interrupt_end() calls schedule, this call to

	 * arch_switch_to_skas isn't needed. We could want to apply this to

	 * improve performance. -bb */

	arch_switch_to_skas(current->thread.prev_sched, current);



	current->thread.prev_sched = NULL;



/* Handle any immediate reschedules or signals */

	interrupt_end();



	userspace(&current->thread.regs.regs);

}

arch/um/sys-i386/ptrace.c

+8 −1
Original line number Diff line number Diff line
@@ -23,7 +23,14 @@ void arch_switch_to_tt(struct task_struct *from, struct task_struct *to) 


void arch_switch_to_skas(struct task_struct *from, struct task_struct *to)

{

	arch_switch_tls_skas(from, to);

	int err = arch_switch_tls_skas(from, to);

	if (!err)

		return;



	if (err != -EINVAL)

		printk(KERN_WARNING "arch_switch_tls_skas failed, errno %d, not EINVAL\n", -err);

	else

		printk(KERN_WARNING "arch_switch_tls_skas failed, errno = EINVAL\n");

}



int is_syscall(unsigned long addr)

arch/um/sys-i386/tls.c

+10 −3
Original line number Diff line number Diff line
@@ -70,8 +70,6 @@ static int get_free_idx(struct task_struct* task) 
	return -ESRCH;

}



#define O_FORCE 1



static inline void clear_user_desc(struct user_desc* info)

{

	/* Postcondition: LDT_empty(info) returns true. */
@@ -84,6 +82,8 @@ static inline void clear_user_desc(struct user_desc* info) 
	info->seg_not_present = 1;

}



#define O_FORCE 1



static int load_TLS(int flags, struct task_struct *to)

{

	int ret = 0;
@@ -162,7 +162,13 @@ void clear_flushed_tls(struct task_struct *task) 
 * SKAS patch. */

int arch_switch_tls_skas(struct task_struct *from, struct task_struct *to)

{

	/* We have no need whatsoever to switch TLS for kernel threads; beyond

	 * that, that would also result in us calling os_set_thread_area with

	 * userspace_pid[cpu] == 0, which gives an error. */

	if (likely(to->mm))

		return load_TLS(O_FORCE, to);



	return 0;

}



int arch_switch_tls_tt(struct task_struct *from, struct task_struct *to)
@@ -324,3 +330,4 @@ int ptrace_get_thread_area(struct task_struct *child, int idx, 
out:

	return ret;

}