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sh: GUSA atomic rollback support.

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This implements kernel-level atomic rollback built on top of gUSA,
as an alternative non-IRQ based atomicity method. This is generally
a faster method for platforms that are lacking the LL/SC pairs that
SH-4A and later use, and is only supportable on legacy cores.

Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
This commit is contained in:
Stuart Menefy
2007-11-30 16:12:36 +09:00
committed by Paul Mundt
parent 53ff09422e
commit 1efe4ce3ca
13 changed files with 590 additions and 180 deletions
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24
arch/sh/kernel/cpu/sh3/entry.S
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@@ -13,8 +13,9 @@
#include <linux/linkage.h>
#include <asm/asm-offsets.h>
#include <asm/thread_info.h>
#include <asm/cpu/mmu_context.h>
#include <asm/unistd.h>
#include <asm/cpu/mmu_context.h>
#include <asm/page.h>
! NOTE:
! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address
@@ -409,6 +410,27 @@ ENTRY(handle_exception)
! Using k0, k1 for scratch registers (r0_bank1, r1_bank),
! save all registers onto stack.
!
#ifdef CONFIG_GUSA
! Check for roll back gRB (User and Kernel)
mov r15, k0
shll k0
bf/s 1f
shll k0
bf/s 1f
stc spc, k1
stc r0_bank, k0
cmp/hs k0, k1 ! test k1 (saved PC) >= k0 (saved r0)
bt/s 2f
stc r1_bank, k1
add #-2, k0
add r15, k0
ldc k0, spc ! PC = saved r0 + r15 - 2
2: mov k1, r15 ! SP = r1
1:
#endif
stc ssr, k0 ! Is it from kernel space?
shll k0 ! Check MD bit (bit30) by shifting it into...
shll k0 ! ...the T bit

19
arch/sh/kernel/entry-common.S
View File

@@ -176,25 +176,6 @@ work_notifysig:
jmp @r1
lds r0, pr
work_resched:
#if defined(CONFIG_GUSA) && !defined(CONFIG_PREEMPT)
! gUSA handling
mov.l @(OFF_SP,r15), r0 ! get user space stack pointer
mov r0, r1
shll r0
bf/s 1f
shll r0
bf/s 1f
mov #OFF_PC, r0
! SP >= 0xc0000000 : gUSA mark
mov.l @(r0,r15), r2 ! get user space PC (program counter)
mov.l @(OFF_R0,r15), r3 ! end point
cmp/hs r3, r2 ! r2 >= r3?
bt 1f
add r3, r1 ! rewind point #2
mov.l r1, @(r0,r15) ! reset PC to rewind point #2
!
1:
#endif
mov.l 1f, r1
jsr @r1 ! schedule
nop

19
arch/sh/kernel/process_32.c
View File

@@ -322,25 +322,6 @@ struct task_struct *__switch_to(struct task_struct *prev,
unlazy_fpu(prev, task_pt_regs(prev));
#endif
#if defined(CONFIG_GUSA) && defined(CONFIG_PREEMPT)
{
struct pt_regs *regs;
preempt_disable();
regs = task_pt_regs(prev);
if (user_mode(regs) && regs->regs[15] >= 0xc0000000) {
int offset = (int)regs->regs[15];
/* Reset stack pointer: clear critical region mark */
regs->regs[15] = regs->regs[1];
if (regs->pc < regs->regs[0])
/* Go to rewind point */
regs->pc = regs->regs[0] + offset;
}
preempt_enable_no_resched();
}
#endif
#ifdef CONFIG_MMU
/*
* Restore the kernel mode register

18
arch/sh/kernel/signal_32.c
View File

@@ -507,24 +507,6 @@ handle_signal(unsigned long sig, struct k_sigaction *ka, siginfo_t *info,
ctrl_inw(regs->pc - 4));
break;
}
#ifdef CONFIG_GUSA
} else {
/* gUSA handling */
preempt_disable();
if (regs->regs[15] >= 0xc0000000) {
int offset = (int)regs->regs[15];
/* Reset stack pointer: clear critical region mark */
regs->regs[15] = regs->regs[1];
if (regs->pc < regs->regs[0])
/* Go to rewind point #1 */
regs->pc = regs->regs[0] + offset -
instruction_size(ctrl_inw(regs->pc-4));
}
preempt_enable_no_resched();
#endif
}
/* Set up the stack frame */