[PATCH] lockdep: irqtrace subsystem, i386 support

Add irqflags-tracing support to i386.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 42 insertions, 4 deletions

diff --git a/arch/i386/Kconfig.debug b/arch/i386/Kconfig.debug
index b20ddd04f3d8..b31c0802e1cc 100644
--- a/arch/i386/Kconfig.debug
+++ b/arch/i386/Kconfig.debug
@@ -1,5 +1,9 @@
 menu "Kernel hacking"
 
+config TRACE_IRQFLAGS_SUPPORT
+        bool
+        default y
+
 source "lib/Kconfig.debug"
 
 config EARLY_PRINTK
diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index 787190c45fdb..d9a260f2efb4 100644
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -42,6 +42,7 @@
 
 #include <linux/linkage.h>
 #include <asm/thread_info.h>
+#include <asm/irqflags.h>
 #include <asm/errno.h>
 #include <asm/segment.h>
 #include <asm/smp.h>
@@ -76,12 +77,21 @@ NT_MASK		= 0x00004000
 VM_MASK         = 0x00020000
 
 #ifdef CONFIG_PREEMPT
-#define preempt_stop            cli
+#define preempt_stop            cli; TRACE_IRQS_OFF
 #else
 #define preempt_stop
 #define resume_kernel           restore_nocheck
 #endif
 
+.macro TRACE_IRQS_IRET
+#ifdef CONFIG_TRACE_IRQFLAGS
+        testl $IF_MASK,EFLAGS(%esp)     # interrupts off?
+        jz 1f
+        TRACE_IRQS_ON
+1:
+#endif
+.endm
+
 #ifdef CONFIG_VM86
 #define resume_userspace_sig    check_userspace
 #else
@@ -257,6 +267,10 @@ ENTRY(sysenter_entry)
         CFI_REGISTER esp, ebp
         movl TSS_sysenter_esp0(%esp),%esp
 sysenter_past_esp:
+        /*
+         * No need to follow this irqs on/off section: the syscall
+         * disabled irqs and here we enable it straight after entry:
+         */
         sti
         pushl $(__USER_DS)
         CFI_ADJUST_CFA_OFFSET 4
@@ -303,6 +317,7 @@ sysenter_past_esp:
         call *sys_call_table(,%eax,4)
         movl %eax,EAX(%esp)
         cli
+        TRACE_IRQS_OFF
         movl TI_flags(%ebp), %ecx
         testw $_TIF_ALLWORK_MASK, %cx
         jne syscall_exit_work
@@ -310,6 +325,7 @@ sysenter_past_esp:
         movl EIP(%esp), %edx
         movl OLDESP(%esp), %ecx
         xorl %ebp,%ebp
+        TRACE_IRQS_ON
         sti
         sysexit
         CFI_ENDPROC
@@ -339,6 +355,7 @@ syscall_exit:
         cli                             # make sure we don't miss an interrupt
                                         # setting need_resched or sigpending
                                         # between sampling and the iret
+        TRACE_IRQS_OFF
         movl TI_flags(%ebp), %ecx
         testw $_TIF_ALLWORK_MASK, %cx   # current->work
         jne syscall_exit_work
@@ -355,12 +372,15 @@ restore_all:
         CFI_REMEMBER_STATE
         je ldt_ss                       # returning to user-space with LDT SS
 restore_nocheck:
+        TRACE_IRQS_IRET
+restore_nocheck_notrace:
         RESTORE_REGS
         addl $4, %esp
         CFI_ADJUST_CFA_OFFSET -4
 1:      iret
 .section .fixup,"ax"
 iret_exc:
+        TRACE_IRQS_ON
         sti
         pushl $0                        # no error code
         pushl $do_iret_error
@@ -386,11 +406,13 @@ ldt_ss:
         subl $8, %esp           # reserve space for switch16 pointer
         CFI_ADJUST_CFA_OFFSET 8
         cli
+        TRACE_IRQS_OFF
         movl %esp, %eax
         /* Set up the 16bit stack frame with switch32 pointer on top,
          * and a switch16 pointer on top of the current frame. */
         call setup_x86_bogus_stack
         CFI_ADJUST_CFA_OFFSET -8        # frame has moved
+        TRACE_IRQS_IRET
         RESTORE_REGS
         lss 20+4(%esp), %esp    # switch to 16bit stack
 1:      iret
@@ -411,6 +433,7 @@ work_resched:
         cli                             # make sure we don't miss an interrupt
                                         # setting need_resched or sigpending
                                         # between sampling and the iret
+        TRACE_IRQS_OFF
         movl TI_flags(%ebp), %ecx
         andl $_TIF_WORK_MASK, %ecx      # is there any work to be done other
                                         # than syscall tracing?
@@ -462,6 +485,7 @@ syscall_trace_entry:
 syscall_exit_work:
         testb $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP), %cl
         jz work_pending
+        TRACE_IRQS_ON
         sti                             # could let do_syscall_trace() call
                                         # schedule() instead
         movl %esp, %eax
@@ -535,9 +559,14 @@ ENTRY(irq_entries_start)
 vector=vector+1
 .endr
 
+/*
+ * the CPU automatically disables interrupts when executing an IRQ vector,
+ * so IRQ-flags tracing has to follow that:
+ */
         ALIGN
 common_interrupt:
         SAVE_ALL
+        TRACE_IRQS_OFF
         movl %esp,%eax
         call do_IRQ
         jmp ret_from_intr
@@ -549,9 +578,10 @@ ENTRY(name)				\
         pushl $~(nr);                   \
         CFI_ADJUST_CFA_OFFSET 4;        \
         SAVE_ALL;                       \
+        TRACE_IRQS_OFF                  \
         movl %esp,%eax;                 \
         call smp_/**/name;              \
-        jmp ret_from_intr;      \
+        jmp ret_from_intr;              \
         CFI_ENDPROC
 
 /* The include is where all of the SMP etc. interrupts come from */
@@ -726,7 +756,7 @@ nmi_stack_correct:
         xorl %edx,%edx          # zero error code
         movl %esp,%eax          # pt_regs pointer
         call do_nmi
-        jmp restore_all
+        jmp restore_nocheck_notrace
         CFI_ENDPROC
 
 nmi_stack_fixup:
diff --git a/arch/i386/kernel/irq.c b/arch/i386/kernel/irq.c
index 16b491703967..6cb529f60dcc 100644
--- a/arch/i386/kernel/irq.c
+++ b/arch/i386/kernel/irq.c
@@ -166,7 +166,7 @@ void irq_ctx_init(int cpu)
         irqctx->tinfo.task              = NULL;
         irqctx->tinfo.exec_domain       = NULL;
         irqctx->tinfo.cpu               = cpu;
-        irqctx->tinfo.preempt_count     = SOFTIRQ_OFFSET;
+        irqctx->tinfo.preempt_count     = 0;
         irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
 
         softirq_ctx[cpu] = irqctx;
@@ -211,6 +211,10 @@ asmlinkage void do_softirq(void)
                         : "0"(isp)
                         : "memory", "cc", "edx", "ecx", "eax"
                 );
+                /*
+                 * Shouldnt happen, we returned above if in_interrupt():
+                 */
+                WARN_ON_ONCE(softirq_count());
         }
 
         local_irq_restore(flags);