2005-11-09 10:04:06 +08:00
|
|
|
#ifndef _ASM_POWERPC_CURRENT_H
|
|
|
|
|
#define _ASM_POWERPC_CURRENT_H
|
2005-12-17 05:43:46 +08:00
|
|
|
#ifdef __KERNEL__
|
2005-11-09 10:04:06 +08:00
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* This program is free software; you can redistribute it and/or
|
|
|
|
|
* modify it under the terms of the GNU General Public License
|
|
|
|
|
* as published by the Free Software Foundation; either version
|
|
|
|
|
* 2 of the License, or (at your option) any later version.
|
|
|
|
|
*/
|
|
|
|
|
|
|
|
|
|
struct task_struct;
|
|
|
|
|
|
|
|
|
|
#ifdef __powerpc64__
|
2007-02-26 03:04:18 +08:00
|
|
|
#include <linux/stddef.h>
|
2005-11-09 10:04:06 +08:00
|
|
|
#include <asm/paca.h>
|
|
|
|
|
|
[POWERPC] Make current preempt-safe
Repeated -j20 kernel builds on a G5 Quad running an SMP PREEMPT kernel
would often collapse within a day, some exec failing with "Bad address".
In each case examined, load_elf_binary was doing a kernel_read, but
generic_file_aio_read's access_ok saw current->thread.fs.seg as USER_DS
instead of KERNEL_DS.
objdump of filemap.o shows gcc 4.1.0 emitting "mr r5,r13 ... ld r9,416(r5)"
here for get_paca()->__current, instead of the expected and much more usual
"ld r9,416(r13)"; I've seen other gcc4s do the same, but perhaps not gcc3s.
So, if the task is preempted and rescheduled on a different cpu in between
the mr and the ld, r5 will be looking at a different paca_struct from the
one it's now on, pick up the wrong __current, and perhaps the wrong seg.
Presumably much worse could happen elsewhere, though that split is rare.
Other architectures appear to be safe (x86_64's read_pda is more limiting
than get_paca), but ppc64 needs to force "current" into one instruction.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
2006-11-01 02:39:31 +08:00
|
|
|
static inline struct task_struct *get_current(void)
|
|
|
|
|
{
|
|
|
|
|
struct task_struct *task;
|
|
|
|
|
|
|
|
|
|
__asm__ __volatile__("ld %0,%1(13)"
|
|
|
|
|
: "=r" (task)
|
|
|
|
|
: "i" (offsetof(struct paca_struct, __current)));
|
|
|
|
|
|
|
|
|
|
return task;
|
|
|
|
|
}
|
|
|
|
|
#define current get_current()
|
2005-11-09 10:04:06 +08:00
|
|
|
|
|
|
|
|
#else
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* We keep `current' in r2 for speed.
|
|
|
|
|
*/
|
|
|
|
|
register struct task_struct *current asm ("r2");
|
|
|
|
|
|
|
|
|
|
#endif
|
|
|
|
|
|
2005-12-17 05:43:46 +08:00
|
|
|
#endif /* __KERNEL__ */
|
2005-11-09 10:04:06 +08:00
|
|
|
#endif /* _ASM_POWERPC_CURRENT_H */
|
