1018.kernel-preempt.patch

sm86xx内核源包括补丁（ GPL ）的

--- linuxmips-2.4.30.ref/arch/ppc/kernel/temp.c	2005-08-29 11:42:15.000000000 -0700
+++ linuxmips-2.4.30/arch/ppc/kernel/temp.c	2005-08-29 11:43:45.000000000 -0700
@@ -138,7 +138,7 @@
 
 static void tau_timeout(void * info)
 {
-	unsigned long cpu = smp_processor_id();
+	unsigned long cpu;
 	unsigned long flags;
 	int size;
 	int shrink;
@@ -146,6 +146,8 @@
 	/* disabling interrupts *should* be okay */
 	save_flags(flags); cli();
 
+	cpu = smp_processor_id();
+
 #ifndef CONFIG_TAU_INT
 	TAUupdate(cpu);
 #endif
@@ -191,13 +193,15 @@
 
 static void tau_timeout_smp(unsigned long unused)
 {
-
 	/* schedule ourselves to be run again */
 	mod_timer(&tau_timer, jiffies + shrink_timer) ;
+
+	preempt_disable();
 #ifdef CONFIG_SMP
 	smp_call_function(tau_timeout, NULL, 1, 0);
 #endif
 	tau_timeout(NULL);
+	preempt_enable();
 }
 
 /*
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/arch/ppc/lib/dec_and_lock.c linuxmips-2.4.30/arch/ppc/lib/dec_and_lock.c
--- linuxmips-2.4.30.ref/arch/ppc/lib/dec_and_lock.c	2005-08-29 11:42:15.000000000 -0700
+++ linuxmips-2.4.30/arch/ppc/lib/dec_and_lock.c	2005-08-29 11:43:45.000000000 -0700
@@ -1,4 +1,5 @@
 #include <linux/module.h>
+#include <linux/sched.h>
 #include <linux/spinlock.h>
 #include <asm/atomic.h>
 #include <asm/system.h>
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/arch/ppc/mm/init.c linuxmips-2.4.30/arch/ppc/mm/init.c
--- linuxmips-2.4.30.ref/arch/ppc/mm/init.c	2005-08-29 11:42:15.000000000 -0700
+++ linuxmips-2.4.30/arch/ppc/mm/init.c	2005-08-29 11:43:45.000000000 -0700
@@ -126,6 +126,9 @@
 int do_check_pgt_cache(int low, int high)
 {
 	int freed = 0;
+
+	preempt_disable();
+
 	if (pgtable_cache_size > high) {
 		do {
                         if (pgd_quicklist) {
@@ -138,6 +141,9 @@
 			}
 		} while (pgtable_cache_size > low);
 	}
+
+	preempt_enable();
+
 	return freed;
 }
 
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/arch/ppc/mm/tlb.c linuxmips-2.4.30/arch/ppc/mm/tlb.c
--- linuxmips-2.4.30.ref/arch/ppc/mm/tlb.c	2005-08-29 11:42:15.000000000 -0700
+++ linuxmips-2.4.30/arch/ppc/mm/tlb.c	2005-08-29 11:43:45.000000000 -0700
@@ -58,11 +58,14 @@
 	 * we can and should dispense with flush_tlb_all().
 	 *  -- paulus.
 	 */
+
+	preempt_disable();
 	local_flush_tlb_range(&init_mm, TASK_SIZE, ~0UL);
 
 #ifdef CONFIG_SMP
 	smp_send_tlb_invalidate(0);
 #endif /* CONFIG_SMP */
+	preempt_enable();
 }
 
 /*
@@ -73,8 +76,10 @@
 void
 local_flush_tlb_mm(struct mm_struct *mm)
 {
+	preempt_disable();
 	if (Hash == 0) {
 		_tlbia();
+		preempt_enable();
 		return;
 	}
 
@@ -88,6 +93,7 @@
 #ifdef CONFIG_SMP
 	smp_send_tlb_invalidate(0);
 #endif
+	preempt_enable();
 }
 
 void
@@ -97,8 +103,10 @@
 	pmd_t *pmd;
 	pte_t *pte;
 
+	preempt_disable();
 	if (Hash == 0) {
 		_tlbie(vmaddr);
+		preempt_enable();
 		return;
 	}
 	mm = (vmaddr < TASK_SIZE)? vma->vm_mm: &init_mm;
@@ -111,6 +119,7 @@
 #ifdef CONFIG_SMP
 	smp_send_tlb_invalidate(0);
 #endif
+	preempt_enable();
 }
 
 
@@ -127,13 +136,17 @@
 	unsigned long pmd_end;
 	unsigned int ctx = mm->context;
 
+	preempt_disable();
 	if (Hash == 0) {
 		_tlbia();
+		preempt_enable();
 		return;
 	}
 	start &= PAGE_MASK;
-	if (start >= end)
+	if (start >= end) {
+		preempt_enable();
 		return;
+	}
 	pmd = pmd_offset(pgd_offset(mm, start), start);
 	do {
 		pmd_end = (start + PGDIR_SIZE) & PGDIR_MASK;
@@ -156,4 +169,5 @@
 #ifdef CONFIG_SMP
 	smp_send_tlb_invalidate(0);
 #endif
+	preempt_enable();
 }
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/CREDITS linuxmips-2.4.30/CREDITS
--- linuxmips-2.4.30.ref/CREDITS	2005-08-29 11:42:15.000000000 -0700
+++ linuxmips-2.4.30/CREDITS	2005-08-29 11:43:45.000000000 -0700
@@ -1007,8 +1007,8 @@
 
 N: Nigel Gamble
 E: [e-mail]
-E: [e-mail]
 D: Interrupt-driven printer driver
+D: Preemptible kernel
 S: 120 Alley Way
 S: Mountain View, California 94040
 S: USA
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/Documentation/Configure.help linuxmips-2.4.30/Documentation/Configure.help
--- linuxmips-2.4.30.ref/Documentation/Configure.help	2005-08-29 11:42:15.000000000 -0700
+++ linuxmips-2.4.30/Documentation/Configure.help	2005-08-29 11:43:45.000000000 -0700
@@ -296,6 +296,17 @@
   If you have a system with several CPUs, you do not need to say Y
   here: the local APIC will be used automatically.
 
+Preemptible Kernel
+CONFIG_PREEMPT
+  This option reduces the latency of the kernel when reacting to
+  real-time or interactive events by allowing a low priority process to
+  be preempted even if it is in kernel mode executing a system call.
+  This allows applications to run more reliably even when the system is
+  under load.
+
+  Say Y here if you are building a kernel for a desktop, embedded or
+  real-time system.  Say N if you are unsure.
+
 Kernel math emulation
 CONFIG_MATH_EMULATION
   Linux can emulate a math coprocessor (used for floating point
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/Documentation/preempt-locking.txt linuxmips-2.4.30/Documentation/preempt-locking.txt
--- linuxmips-2.4.30.ref/Documentation/preempt-locking.txt	1969-12-31 16:00:00.000000000 -0800
+++ linuxmips-2.4.30/Documentation/preempt-locking.txt	2005-08-29 11:43:45.000000000 -0700
@@ -0,0 +1,104 @@
+		  Proper Locking Under a Preemptible Kernel:
+		       Keeping Kernel Code Preempt-Safe
+			  Robert Love <[e-mail]>
+			   Last Updated: 22 Jan 2002
+
+
+INTRODUCTION
+
+
+A preemptible kernel creates new locking issues.  The issues are the same as
+those under SMP: concurrency and reentrancy.  Thankfully, the Linux preemptible
+kernel model leverages existing SMP locking mechanisms.  Thus, the kernel
+requires explicit additional locking for very few additional situations.
+
+This document is for all kernel hackers.  Developing code in the kernel
+requires protecting these situations.
+ 
+
+RULE #1: Per-CPU data structures need explicit protection
+
+
+Two similar problems arise. An example code snippet:
+
+	struct this_needs_locking tux[NR_CPUS];
+	tux[smp_processor_id()] = some_value;
+	/* task is preempted here... */
+	something = tux[smp_processor_id()];
+
+First, since the data is per-CPU, it may not have explicit SMP locking, but
+require it otherwise.  Second, when a preempted task is finally rescheduled,
+the previous value of smp_processor_id may not equal the current.  You must
+protect these situations by disabling preemption around them.
+
+
+RULE #2: CPU state must be protected.
+
+
+Under preemption, the state of the CPU must be protected.  This is arch-
+dependent, but includes CPU structures and state not preserved over a context
+switch.  For example, on x86, entering and exiting FPU mode is now a critical
+section that must occur while preemption is disabled.  Think what would happen
+if the kernel is executing a floating-point instruction and is then preempted.
+Remember, the kernel does not save FPU state except for user tasks.  Therefore,
+upon preemption, the FPU registers will be sold to the lowest bidder.  Thus,
+preemption must be disabled around such regions.
+
+Note, some FPU functions are already explicitly preempt safe.  For example,
+kernel_fpu_begin and kernel_fpu_end will disable and enable preemption.
+However, math_state_restore must be called with preemption disabled.
+
+
+RULE #3: Lock acquire and release must be performed by same task
+
+
+A lock acquired in one task must be released by the same task.  This
+means you can't do oddball things like acquire a lock and go off to
+play while another task releases it.  If you want to do something
+like this, acquire and release the task in the same code path and
+have the caller wait on an event by the other task.
+
+
+SOLUTION
+
+
+Data protection under preemption is achieved by disabling preemption for the
+duration of the critical region.
+
+preempt_enable()		decrement the preempt counter
+preempt_disable()		increment the preempt counter
+preempt_enable_no_resched()	decrement, but do not immediately preempt
+preempt_get_count()		return the preempt counter
+
+The functions are nestable.  In other words, you can call preempt_disable
+n-times in a code path, and preemption will not be reenabled until the n-th
+call to preempt_enable.  The preempt statements define to nothing if
+preemption is not enabled.
+
+Note that you do not need to explicitly prevent preemption if you are holding
+any locks or interrupts are disabled, since preemption is implicitly disabled
+in those cases.
+
+Example:
+
+	cpucache_t *cc; /* this is per-CPU */
+	preempt_disable();
+	cc = cc_data(searchp);
+	if (cc && cc->avail) {
+		__free_block(searchp, cc_entry(cc), cc->avail);
+		cc->avail = 0;
+	}
+	preempt_enable();
+	return 0;
+
+Notice how the preemption statements must encompass every reference of the
+critical variables.  Another example:
+
+	int buf[NR_CPUS];
+	set_cpu_val(buf);
+	if (buf[smp_processor_id()] == -1) printf(KERN_INFO "wee!\n");
+	spin_lock(&buf_lock);
+	/* ... */
+
+This code is not preempt-safe, but see how easily we can fix it by simply
+moving the spin_lock up two lines.
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/drivers/ieee1394/csr.c linuxmips-2.4.30/drivers/ieee1394/csr.c
--- linuxmips-2.4.30.ref/drivers/ieee1394/csr.c	2005-08-29 11:42:15.000000000 -0700
+++ linuxmips-2.4.30/drivers/ieee1394/csr.c	2005-08-29 11:43:45.000000000 -0700
@@ -18,6 +18,7 @@
  */