[PATCH]Preemption patch for 2.6

[Manish Lachwani <mlachwani@mvista.com>]

Hello !

The attached patch incorporates preemption enable/disable in some parts
of the kernel. I have tested this on the Broadcom Sibyte. Please review
...

Thanks
Manish Lachwani

Index: linux-2.6.8.1/arch/mips/kernel/signal32.c
===================================================================
--- linux-2.6.8.1.orig/arch/mips/kernel/signal32.c
+++ linux-2.6.8.1/arch/mips/kernel/signal32.c
@@ -295,6 +295,8 @@
 
        err |= __get_user(current->used_math, &sc->sc_used_math);
 
+       preempt_disable();
+
        if (current->used_math) {
                /* restore fpu context if we have used it before */
                own_fpu();
@@ -304,6 +306,8 @@
                lose_fpu();
        }
 
+       preempt_enable();
+
        return err;
 }
 
@@ -489,12 +493,16 @@
         * Save FPU state to signal context.  Signal handler will "inherit"
         * current FPU state.
         */
+       preempt_disable();
+
        if (!is_fpu_owner()) {
                own_fpu();
                restore_fp(current);
        }
        err |= save_fp_context32(sc);
 
+       preempt_enable();
+
 out:
        return err;
 }
Index: linux-2.6.8.1/arch/mips/mm/c-sb1.c
===================================================================
--- linux-2.6.8.1.orig/arch/mips/mm/c-sb1.c
+++ linux-2.6.8.1/arch/mips/mm/c-sb1.c
@@ -197,10 +197,14 @@
        if (!(vma->vm_flags & VM_EXEC))
                return;
 
+       preempt_disable();
+
        addr &= PAGE_MASK;
        args.vma = vma;
        args.addr = addr;
        on_each_cpu(sb1_flush_cache_page_ipi, (void *) &args, 1, 1);
+
+       preempt_enable();
 }
 #else
 void sb1_flush_cache_page(struct vm_area_struct *vma, unsigned long
addr)
@@ -243,7 +247,9 @@
 
 static void sb1___flush_cache_all(void)
 {
+       preempt_disable();
        on_each_cpu(sb1___flush_cache_all_ipi, 0, 1, 1);
+       preempt_enable();
 }
 #else
 void sb1___flush_cache_all(void)
@@ -291,9 +297,13 @@
 {
        struct flush_icache_range_args args;
 
+       preempt_disable();
+
        args.start = start;
        args.end = end;
        on_each_cpu(sb1_flush_icache_range_ipi, &args, 1, 1);
+
+       preempt_enable();
 }
 #else
 void sb1_flush_icache_range(unsigned long start, unsigned long end)
@@ -348,9 +358,14 @@
 
        if (!(vma->vm_flags & VM_EXEC))
                return;
+
+       preempt_disable();
+
        args.vma = vma;
        args.page = page;
        on_each_cpu(sb1_flush_icache_page_ipi, (void *) &args, 1, 1);
+
+       preempt_enable();
 }
 #else
 void sb1_flush_icache_page(struct vm_area_struct *vma, struct page
*page)
@@ -377,7 +392,9 @@
 
 static void sb1_flush_cache_sigtramp(unsigned long addr)
 {
+       preempt_disable();
        on_each_cpu(sb1_flush_cache_sigtramp_ipi, (void *) addr, 1, 1);
+       preempt_enable();
 }
 #else
 void sb1_flush_cache_sigtramp(unsigned long addr)
Index: linux-2.6.8.1/arch/mips/mm/tlb-sb1.c
===================================================================
--- linux-2.6.8.1.orig/arch/mips/mm/tlb-sb1.c
+++ linux-2.6.8.1/arch/mips/mm/tlb-sb1.c
@@ -286,10 +286,17 @@
    these entries, we just bump the asid. */
 void local_flush_tlb_mm(struct mm_struct *mm)
 {
-       int cpu = smp_processor_id();
+       int cpu;
+
+       preempt_disable();
+
+       cpu = smp_processor_id();
+
        if (cpu_context(cpu, mm) != 0) {
                drop_mmu_context(mm, cpu);
        }
+
+       preempt_enable();
 }
 
 /* Stolen from mips32 routines */
Index: linux-2.6.8.1/arch/mips/kernel/traps.c
===================================================================
--- linux-2.6.8.1.orig/arch/mips/kernel/traps.c
+++ linux-2.6.8.1/arch/mips/kernel/traps.c
@@ -411,6 +411,8 @@
                goto sig;
        }
 
+       preempt_disable();
+
        if (ll_task == NULL || ll_task == current) {
                ll_bit = 1;
        } else {
@@ -418,6 +420,8 @@
        }
        ll_task = current;
 
+       preempt_enable();
+
        regs->regs[(opcode & RT) >> 16] = value;
 
        compute_return_epc(regs);
@@ -450,12 +454,18 @@
                signal = SIGBUS;
                goto sig;
        }
+
+       preempt_disable();
+
        if (ll_bit == 0 || ll_task != current) {
                regs->regs[reg] = 0;
+               preempt_enable();
                compute_return_epc(regs);
                return;
        }
 
+       preempt_enable();
+
        if (put_user(regs->regs[reg], vaddr)) {
                signal = SIGSEGV;
                goto sig;
@@ -515,6 +525,8 @@
        if (fcr31 & FPU_CSR_UNI_X) {
                int sig;
 
+               preempt_disable();
+
                /*
                 * Unimplemented operation exception.  If we've got the full
                 * software emulator on-board, let's use it...
@@ -540,6 +552,8 @@
                /* Restore the hardware register state */
                restore_fp(current);
 
+               preempt_enable();
+
                /* If something went wrong, signal */
                if (sig)
                        force_sig(sig, current);
@@ -659,6 +673,8 @@
                break;
 
        case 1:
+               preempt_disable();
+
                own_fpu();
                if (current->used_math) {       /* Using the FPU again.  */
                        restore_fp(current);
@@ -674,6 +690,8 @@
                                force_sig(sig, current);
                }
 
+               preempt_enable();
+
                return;
 
        case 2:
Index: linux-2.6.8.1/arch/mips/kernel/process.c
===================================================================
--- linux-2.6.8.1.orig/arch/mips/kernel/process.c
+++ linux-2.6.8.1/arch/mips/kernel/process.c
@@ -99,10 +99,14 @@
 
        childksp = (unsigned long)ti + THREAD_SIZE - 32;
 
+       preempt_disable();
+
        if (is_fpu_owner()) {
                save_fp(p);
        }
 
+       preempt_enable();
+
        /* set up new TSS. */
        childregs = (struct pt_regs *) childksp - 1;
        *childregs = *regs;
Index: linux-2.6.8.1/arch/mips/kernel/signal.c
===================================================================
--- linux-2.6.8.1.orig/arch/mips/kernel/signal.c
+++ linux-2.6.8.1/arch/mips/kernel/signal.c
@@ -178,6 +178,8 @@
 
        err |= __get_user(current->used_math, &sc->sc_used_math);
 
+       preempt_disable();
+
        if (current->used_math) {
                /* restore fpu context if we have used it before */
                own_fpu();
@@ -187,6 +189,8 @@
                lose_fpu();
        }
 
+       preempt_enable();
+
        return err;
 }
 
@@ -320,12 +324,16 @@
         * Save FPU state to signal context.  Signal handler will "inherit"
         * current FPU state.
         */
+       preempt_disable();
+
        if (!is_fpu_owner()) {
                own_fpu();
                restore_fp(current);
        }
        err |= save_fp_context(sc);
 
+       preempt_enable();
+
 out:
        return err;
 }