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Subjectsoftirq bugs in pre2
in pre2 ret_from_exception reschedule and handle signals even if it is
returning to kernel code. rescheduling was not so obviously broken (at
least not for the page fault ;) but it just slowdown the code as I just
have all the necessary explicit checks in copy-user itself (which are
needed anyways exactly because there may not be any page fault).

diff -urN 2.4.6pre2/arch/i386/kernel/entry.S softirq-smp-fixes/arch/i386/kernel/entry.S
--- 2.4.6pre2/arch/i386/kernel/entry.S Sat Jun 9 00:04:47 2001
+++ softirq-smp-fixes/arch/i386/kernel/entry.S Mon Jun 11 19:25:06 2001
@@ -246,16 +246,9 @@
jmp ret_from_sys_call

ALIGN
-ret_from_exception:
- cli
- cmpl $0,need_resched(%ebx)
- jne reschedule
- cmpl $0,sigpending(%ebx)
- jne signal_return
- jmp restore_all
-
ENTRY(ret_from_intr)
GET_CURRENT(%ebx)
+ret_from_exception:
movl EFLAGS(%esp),%eax # mix EFLAGS and CS
movb CS(%esp),%al
testl $(VM_MASK | 3),%eax # return to VM86 mode or non-supervisor?
@@ -313,14 +306,16 @@
pushl $-1 # mark this as an int
SAVE_ALL
GET_CURRENT(%ebx)
- pushl $ret_from_exception
movl %cr0,%eax
testl $0x4,%eax # EM (math emulation bit)
- je SYMBOL_NAME(math_state_restore)
+ jne device_not_available_emulate
+ call SYMBOL_NAME(math_state_restore)
+ jmp ret_from_exception
+device_not_available_emulate:
pushl $0 # temporary storage for ORIG_EIP
call SYMBOL_NAME(math_emulate)
addl $4,%esp
- ret
+ jmp ret_from_exception

ENTRY(debug)
pushl $0
(side note, I also removed the call prediction invalidation so fpu
restore is faster)

Since I mentioned the copy-user latency fixes (even if offtopic with the
above) this is the URL for trivial merging:

ftp://ftp.us.kernel.org/pub/linux/kernel/people/andrea/kernels/v2.4/2.4.5aa3/00_copy-user-lat-2

00_copy-user-lat-2:

diff -urN 2.4.4/arch/i386/lib/usercopy.c lowlat/arch/i386/lib/usercopy.c
--- 2.4.4/arch/i386/lib/usercopy.c Sat Apr 28 05:24:30 2001
+++ lowlat/arch/i386/lib/usercopy.c Sun Apr 29 18:33:13 2001
@@ -6,6 +6,7 @@
* Copyright 1997 Linus Torvalds
*/
#include <linux/config.h>
+#include <linux/condsched.h>
#include <asm/uaccess.h>
#include <asm/mmx.h>

@@ -91,6 +92,7 @@
"=&D" (__d2) \
: "i"(-EFAULT), "0"(count), "1"(count), "3"(src), "4"(dst) \
: "memory"); \
+ conditional_schedule(); \
} while (0)

long
@@ -134,6 +136,7 @@
".previous" \
: "=&c"(size), "=&D" (__d0) \
: "r"(size & 3), "0"(size / 4), "1"(addr), "a"(0)); \
+ conditional_schedule(); \
} while (0)

unsigned long
@@ -180,5 +183,6 @@
:"=r" (n), "=D" (s), "=a" (res), "=c" (tmp)
:"0" (n), "1" (s), "2" (0), "3" (mask)
:"cc");
+ conditional_schedule();
return res & mask;
}
diff -urN 2.4.4/include/asm-alpha/uaccess.h lowlat/include/asm-alpha/uaccess.h
--- 2.4.4/include/asm-alpha/uaccess.h Sun Apr 1 20:11:14 2001
+++ lowlat/include/asm-alpha/uaccess.h Sun Apr 29 18:33:15 2001
@@ -3,6 +3,7 @@

#include <linux/errno.h>
#include <linux/sched.h>
+#include <linux/condsched.h>


/*
@@ -384,19 +385,36 @@
return len;
}

-#define __copy_to_user(to,from,n) __copy_tofrom_user_nocheck((to),(from),(n))
-#define __copy_from_user(to,from,n) __copy_tofrom_user_nocheck((to),(from),(n))
+static inline long
+__copy_to_user(void *to, const void *from, long n)
+{
+ n = __copy_tofrom_user_nocheck(to, from, n);
+ conditional_schedule();
+ return n;
+}
+
+static inline long
+__copy_from_user(void *to, const void *from, long n)
+{
+ n = __copy_tofrom_user_nocheck(to, from, n);
+ conditional_schedule();
+ return n;
+}

extern inline long
copy_to_user(void *to, const void *from, long n)
{
- return __copy_tofrom_user(to, from, n, to);
+ n = __copy_tofrom_user(to, from, n, to);
+ conditional_schedule();
+ return n;
}

extern inline long
copy_from_user(void *to, const void *from, long n)
{
- return __copy_tofrom_user(to, from, n, from);
+ n = __copy_tofrom_user(to, from, n, from);
+ conditional_schedule();
+ return n;
}

extern void __do_clear_user(void);
@@ -434,6 +452,7 @@
: "$1","$2","$3","$4","$5","$28","memory");
len = __cl_len;
}
+ conditional_schedule();
return len;
}

@@ -448,6 +467,7 @@
long ret = -EFAULT;
if (__access_ok((long)from, 0, get_fs()))
ret = __strncpy_from_user(to, from, n);
+ conditional_schedule();
return ret;
}

@@ -456,7 +476,11 @@

extern inline long strlen_user(const char *str)
{
- return access_ok(VERIFY_READ,str,0) ? __strlen_user(str) : 0;
+ long ret = 0;
+ if (access_ok(VERIFY_READ,str,0))
+ ret = __strlen_user(str);
+ conditional_schedule();
+ return ret;
}

/* Returns: 0 if exception before NUL or reaching the supplied limit (N),
@@ -465,7 +489,11 @@

extern inline long strnlen_user(const char *str, long n)
{
- return access_ok(VERIFY_READ,str,0) ? __strnlen_user(str, n) : 0;
+ long ret = 0;
+ if (access_ok(VERIFY_READ,str,0))
+ ret = __strnlen_user(str, n);
+ conditional_schedule();
+ return ret;
}

/*
diff -urN 2.4.4/include/asm-i386/uaccess.h lowlat/include/asm-i386/uaccess.h
--- 2.4.4/include/asm-i386/uaccess.h Sat Apr 28 05:24:45 2001
+++ lowlat/include/asm-i386/uaccess.h Sun Apr 29 18:33:13 2001
@@ -6,6 +6,7 @@
*/
#include <linux/config.h>
#include <linux/sched.h>
+#include <linux/condsched.h>
#include <asm/page.h>

#define VERIFY_READ 0
@@ -258,6 +259,7 @@
: "=&c"(size), "=&D" (__d0), "=&S" (__d1) \
: "r"(size & 3), "0"(size / 4), "1"(to), "2"(from) \
: "memory"); \
+ conditional_schedule(); \
} while (0)

#define __copy_user_zeroing(to,from,size) \
@@ -286,6 +288,7 @@
: "=&c"(size), "=&D" (__d0), "=&S" (__d1) \
: "r"(size & 3), "0"(size / 4), "1"(to), "2"(from) \
: "memory"); \
+ conditional_schedule(); \
} while (0)

/* We let the __ versions of copy_from/to_user inline, because they're often
@@ -326,6 +329,7 @@
: "=c"(size), "=&S" (__d0), "=&D" (__d1)\
: "1"(from), "2"(to), "0"(size/4) \
: "memory"); \
+ conditional_schedule(); \
break; \
case 1: \
__asm__ __volatile__( \
@@ -416,6 +420,7 @@
: "=c"(size), "=&S" (__d0), "=&D" (__d1)\
: "1"(from), "2"(to), "0"(size/4) \
: "memory"); \
+ conditional_schedule(); \
break; \
case 1: \
__asm__ __volatile__( \
diff -urN 2.4.4/include/linux/condsched.h lowlat/include/linux/condsched.h
--- 2.4.4/include/linux/condsched.h Thu Jan 1 01:00:00 1970
+++ lowlat/include/linux/condsched.h Sun Apr 29 18:33:13 2001
@@ -0,0 +1,14 @@
+#ifndef _LINUX_CONDSCHED_H
+#define _LINUX_CONDSCHED_H
+
+#ifndef __ASSEMBLY__
+#define conditional_schedule() \
+do { \
+ if (current->need_resched) { \
+ current->state = TASK_RUNNING; \
+ schedule(); \
+ } \
+} while(0)
+#endif
+
+#endif


Andrea
-
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