* [PATCH] FRV: Make switch_to() return previous task
@ 2005-02-04 17:30 David Howells
0 siblings, 0 replies; only message in thread
From: David Howells @ 2005-02-04 17:30 UTC (permalink / raw)
To: torvalds, akpm; +Cc: linux-kernel
The attached patch makes switch_to() on the FRV pass through and return the
previous task pointer rather than trusting to luck that it'll be left in the
correct register/variable.
Signed-Off-By: David Howells <dhowells@redhat.com>
---
warthog>diffstat -p1 frv-switchto-2611rc3.diff
arch/frv/kernel/entry.S | 3 +--
arch/frv/kernel/switch_to.S | 34 ++++++++++++++++++++++------------
include/asm-frv/processor.h | 2 +-
include/asm-frv/system.h | 17 ++++++++++-------
4 files changed, 34 insertions(+), 22 deletions(-)
diff -uNrp /warthog/kernels/linux-2.6.11-rc3/arch/frv/kernel/entry.S linux-2.6.11-rc3-frv/arch/frv/kernel/entry.S
--- /warthog/kernels/linux-2.6.11-rc3/arch/frv/kernel/entry.S 2005-02-04 11:49:30.000000000 +0000
+++ linux-2.6.11-rc3-frv/arch/frv/kernel/entry.S 2005-02-04 15:30:45.000000000 +0000
@@ -782,13 +782,12 @@ __entry_do_NMI:
###############################################################################
#
# the return path for a newly forked child process
-# - __switch_to() saved the old current pointer in GR27 for us
+# - __switch_to() saved the old current pointer in GR8 for us
#
###############################################################################
.globl ret_from_fork
ret_from_fork:
LEDS 0x6100
- ori.p gr27,0,gr8
call schedule_tail
# fork & co. return 0 to child
diff -uNrp /warthog/kernels/linux-2.6.11-rc3/arch/frv/kernel/switch_to.S linux-2.6.11-rc3-frv/arch/frv/kernel/switch_to.S
--- /warthog/kernels/linux-2.6.11-rc3/arch/frv/kernel/switch_to.S 2005-02-04 11:49:30.000000000 +0000
+++ linux-2.6.11-rc3-frv/arch/frv/kernel/switch_to.S 2005-02-04 15:31:14.000000000 +0000
@@ -43,20 +43,22 @@ __kernel_current_task:
###############################################################################
#
-# struct task_struct *__switch_to(struct thread_struct *prev, struct thread_struct *next)
+# struct task_struct *__switch_to(struct thread_struct *prev_thread,
+# struct thread_struct *next_thread,
+# struct task_struct *prev)
#
###############################################################################
.globl __switch_to
__switch_to:
# save outgoing process's context
- sethi.p %hi(__switch_back),gr11
- setlo %lo(__switch_back),gr11
- movsg lr,gr10
+ sethi.p %hi(__switch_back),gr13
+ setlo %lo(__switch_back),gr13
+ movsg lr,gr12
stdi gr28,@(gr8,#__THREAD_FRAME)
sti sp ,@(gr8,#__THREAD_SP)
sti fp ,@(gr8,#__THREAD_FP)
- stdi gr10,@(gr8,#__THREAD_LR)
+ stdi gr12,@(gr8,#__THREAD_LR)
stdi gr16,@(gr8,#__THREAD_GR(16))
stdi gr18,@(gr8,#__THREAD_GR(18))
stdi gr20,@(gr8,#__THREAD_GR(20))
@@ -68,14 +70,14 @@ __switch_to:
ldi.p @(gr8,#__THREAD_USER),gr8
call save_user_regs
or gr22,gr22,gr8
-
+
# retrieve the new context
sethi.p %hi(__kernel_frame0_ptr),gr6
setlo %lo(__kernel_frame0_ptr),gr6
movsg psr,gr4
lddi.p @(gr9,#__THREAD_FRAME),gr10
- or gr29,gr29,gr27 ; ret_from_fork needs to know old current
+ or gr10,gr10,gr27 ; save prev for the return value
ldi @(gr11,#4),gr19 ; get new_current->thread_info
@@ -88,8 +90,8 @@ __switch_to:
andi gr4,#~PSR_ET,gr5
movgs gr5,psr
- or.p gr10,gr0,gr28
- or gr11,gr0,gr29
+ or.p gr10,gr0,gr28 ; set __frame
+ or gr11,gr0,gr29 ; set __current
or.p gr12,gr0,sp
or gr13,gr0,fp
or gr19,gr0,gr15 ; set __current_thread_info
@@ -108,14 +110,17 @@ __switch_to:
111:
# jump to __switch_back or ret_from_fork as appropriate
+ # - move prev to GR8
movgs gr4,psr
- jmpl @(gr18,gr0)
+ jmpl.p @(gr18,gr0)
+ or gr27,gr27,gr8
###############################################################################
#
# restore incoming process's context
# - on entry:
# - SP, FP, LR, GR15, GR28 and GR29 will have been set up appropriately
+# - GR8 will point to the outgoing task_struct
# - GR9 will point to the incoming thread_struct
#
###############################################################################
@@ -128,12 +133,16 @@ __switch_back:
lddi @(gr9,#__THREAD_GR(26)),gr26
# fall through into restore_user_regs()
- ldi @(gr9,#__THREAD_USER),gr8
+ ldi.p @(gr9,#__THREAD_USER),gr8
+ or gr8,gr8,gr9
###############################################################################
#
# restore extra general regs and FP/Media regs
-# - void restore_user_regs(const struct user_context *target)
+# - void *restore_user_regs(const struct user_context *target, void *retval)
+# - on entry:
+# - GR8 will point to the user context to swap in
+# - GR9 will contain the value to be returned in GR8 (prev task on context switch)
#
###############################################################################
.globl restore_user_regs
@@ -245,6 +254,7 @@ __restore_skip_fr32_fr63:
lddi @(gr8,#__FPMEDIA_FNER(0)),gr4
movsg fner0,gr4
movsg fner1,gr5
+ or.p gr9,gr9,gr8
bralr
# the FR451 also has ACC8-11/ACCG8-11 regs (but not 4-7...)
diff -uNrp /warthog/kernels/linux-2.6.11-rc3/include/asm-frv/processor.h linux-2.6.11-rc3-frv/include/asm-frv/processor.h
--- /warthog/kernels/linux-2.6.11-rc3/include/asm-frv/processor.h 2005-02-04 11:50:21.000000000 +0000
+++ linux-2.6.11-rc3-frv/include/asm-frv/processor.h 2005-02-04 15:33:28.484022068 +0000
@@ -113,7 +113,7 @@ static inline void release_thread(struct
extern asmlinkage int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags);
extern asmlinkage void save_user_regs(struct user_context *target);
-extern asmlinkage void restore_user_regs(const struct user_context *target);
+extern asmlinkage void *restore_user_regs(const struct user_context *target, ...);
#define copy_segments(tsk, mm) do { } while (0)
#define release_segments(mm) do { } while (0)
diff -uNrp /warthog/kernels/linux-2.6.11-rc3/include/asm-frv/system.h linux-2.6.11-rc3-frv/include/asm-frv/system.h
--- /warthog/kernels/linux-2.6.11-rc3/include/asm-frv/system.h 2005-02-04 11:50:21.000000000 +0000
+++ linux-2.6.11-rc3-frv/include/asm-frv/system.h 2005-02-04 16:12:47.113598875 +0000
@@ -26,13 +26,16 @@ struct thread_struct;
* The `mb' is to tell GCC not to cache `current' across this call.
*/
extern asmlinkage
-void __switch_to(struct thread_struct *prev, struct thread_struct *next);
-
-#define switch_to(prev, next, last) \
-do { \
- prev->thread.sched_lr = (unsigned long) __builtin_return_address(0); \
- __switch_to(&prev->thread, &next->thread); \
- mb(); \
+struct task_struct *__switch_to(struct thread_struct *prev_thread,
+ struct thread_struct *next_thread,
+ struct task_struct *prev);
+
+#define switch_to(prev, next, last) \
+do { \
+ (prev)->thread.sched_lr = \
+ (unsigned long) __builtin_return_address(0); \
+ (last) = __switch_to(&(prev)->thread, &(next)->thread, (prev)); \
+ mb(); \
} while(0)
/*
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2005-02-04 17:30 [PATCH] FRV: Make switch_to() return previous task David Howells
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