6b8019c85e
ret_from_fork is always entered with hw interrupts off, which prevents real-time domains to preempt the Linux kernel during part of the initial context switch to the new task, which could in turn raise the worst-case latency figures. To avoid this, stall the root domain stage in the interrupt pipeline to keep the scheduling tail code free from Linux-handled IRQs, then enable hardware interrupts again. Signed-off-by: Philippe Gerum <rpm@xenomai.org> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
131 lines
2.8 KiB
ArmAsm
131 lines
2.8 KiB
ArmAsm
/*
|
|
* File: arch/blackfin/kernel/entry.S
|
|
* Based on:
|
|
* Author:
|
|
*
|
|
* Created:
|
|
* Description:
|
|
*
|
|
* Modified:
|
|
* Copyright 2004-2006 Analog Devices Inc.
|
|
*
|
|
* Bugs: Enter bugs at http://blackfin.uclinux.org/
|
|
*
|
|
* 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.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, see the file COPYING, or write
|
|
* to the Free Software Foundation, Inc.,
|
|
* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*/
|
|
|
|
#include <linux/linkage.h>
|
|
#include <asm/thread_info.h>
|
|
#include <asm/errno.h>
|
|
#include <asm/blackfin.h>
|
|
#include <asm/asm-offsets.h>
|
|
|
|
#include <asm/context.S>
|
|
|
|
#ifdef CONFIG_EXCPT_IRQ_SYSC_L1
|
|
.section .l1.text
|
|
#else
|
|
.text
|
|
#endif
|
|
|
|
ENTRY(_ret_from_fork)
|
|
#ifdef CONFIG_IPIPE
|
|
/*
|
|
* Hw IRQs are off on entry, and we don't want the scheduling tail
|
|
* code to starve high priority domains from interrupts while it
|
|
* runs. Therefore we first stall the root stage to have the
|
|
* virtual interrupt state reflect IMASK.
|
|
*/
|
|
p0.l = ___ipipe_root_status;
|
|
p0.h = ___ipipe_root_status;
|
|
r4 = [p0];
|
|
bitset(r4, 0);
|
|
[p0] = r4;
|
|
/*
|
|
* Then we may enable hw IRQs, allowing preemption from high
|
|
* priority domains. schedule_tail() will do local_irq_enable()
|
|
* since Blackfin does not define __ARCH_WANT_UNLOCKED_CTXSW, so
|
|
* there is no need to unstall the root domain by ourselves
|
|
* afterwards.
|
|
*/
|
|
p0.l = _bfin_irq_flags;
|
|
p0.h = _bfin_irq_flags;
|
|
r4 = [p0];
|
|
sti r4;
|
|
#endif /* CONFIG_IPIPE */
|
|
SP += -12;
|
|
call _schedule_tail;
|
|
SP += 12;
|
|
r0 = [sp + PT_IPEND];
|
|
cc = bittst(r0,1);
|
|
if cc jump .Lin_kernel;
|
|
RESTORE_CONTEXT
|
|
rti;
|
|
.Lin_kernel:
|
|
bitclr(r0,1);
|
|
[sp + PT_IPEND] = r0;
|
|
/* do a 'fake' RTI by jumping to [RETI]
|
|
* to avoid clearing supervisor mode in child
|
|
*/
|
|
r0 = [sp + PT_PC];
|
|
[sp + PT_P0] = r0;
|
|
|
|
RESTORE_ALL_SYS
|
|
jump (p0);
|
|
ENDPROC(_ret_from_fork)
|
|
|
|
ENTRY(_sys_fork)
|
|
r0 = -EINVAL;
|
|
#if (ANOMALY_05000371)
|
|
nop;
|
|
nop;
|
|
nop;
|
|
#endif
|
|
rts;
|
|
ENDPROC(_sys_fork)
|
|
|
|
ENTRY(_sys_vfork)
|
|
r0 = sp;
|
|
r0 += 24;
|
|
[--sp] = rets;
|
|
SP += -12;
|
|
call _bfin_vfork;
|
|
SP += 12;
|
|
rets = [sp++];
|
|
rts;
|
|
ENDPROC(_sys_vfork)
|
|
|
|
ENTRY(_sys_clone)
|
|
r0 = sp;
|
|
r0 += 24;
|
|
[--sp] = rets;
|
|
SP += -12;
|
|
call _bfin_clone;
|
|
SP += 12;
|
|
rets = [sp++];
|
|
rts;
|
|
ENDPROC(_sys_clone)
|
|
|
|
ENTRY(_sys_rt_sigreturn)
|
|
r0 = sp;
|
|
r0 += 24;
|
|
[--sp] = rets;
|
|
SP += -12;
|
|
call _do_rt_sigreturn;
|
|
SP += 12;
|
|
rets = [sp++];
|
|
rts;
|
|
ENDPROC(_sys_rt_sigreturn)
|