Adjust the order of operations in spinlock_enter() and spinlock_exit() to

work properly with single-stepping in a kernel debugger.  Specifically,
these routines have always disabled interrupts before increasing the nesting
count and restored the prior state of interrupts after decreasing the nesting
count to avoid problems with a nested interrupt not disabling interrupts
when acquiring a spin lock.  However, trap interrupts for single-stepping
can still occur even when interrupts are disabled.  Now the saved state of
interrupts is not saved in the thread until after interrupts have been
disabled and the nesting count has been increased.  Similarly, the saved
state from the thread cannot be read once the nesting count has been
decreased to zero.  To fix this, use temporary variables to store interrupt
state and shuffle it between the thread's MD area and the appropriate
registers.

In cooperation with:	bde
MFC after:     1 month

10 files changed, 93 insertions, 41 deletions

diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index eba788f..738427f 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -1762,11 +1762,15 @@ void
 spinlock_enter(void)
 {
 	struct thread *td;
+	register_t flags;
 
 	td = curthread;
-	if (td->td_md.md_spinlock_count == 0)
-		td->td_md.md_saved_flags = intr_disable();
-	td->td_md.md_spinlock_count++;
+	if (td->td_md.md_spinlock_count == 0) {
+		flags = intr_disable();
+		td->td_md.md_spinlock_count = 1;
+		td->td_md.md_saved_flags = flags;
+	} else
+		td->td_md.md_spinlock_count++;
 	critical_enter();
 }
 
@@ -1774,12 +1778,14 @@ void
 spinlock_exit(void)
 {
 	struct thread *td;
+	register_t flags;
 
 	td = curthread;
 	critical_exit();
+	flags = td->td_md.md_saved_flags;
 	td->td_md.md_spinlock_count--;
 	if (td->td_md.md_spinlock_count == 0)
-		intr_restore(td->td_md.md_saved_flags);
+		intr_restore(flags);
 }
 
 /*
diff --git a/sys/arm/arm/machdep.c b/sys/arm/arm/machdep.c
index 32348d7..2d26f68 100644
--- a/sys/arm/arm/machdep.c
+++ b/sys/arm/arm/machdep.c
@@ -493,11 +493,15 @@ void
 spinlock_enter(void)
 {
 	struct thread *td;
+	register_t cspr;
 
 	td = curthread;
-	if (td->td_md.md_spinlock_count == 0)
-		td->td_md.md_saved_cspr = disable_interrupts(I32_bit | F32_bit);
-	td->td_md.md_spinlock_count++;
+	if (td->td_md.md_spinlock_count == 0) {
+		cspr = disable_interrupts(I32_bit | F32_bit);
+		td->td_md.md_spinlock_count = 1;
+		td->td_md.md_saved_cspr = cspr;
+	} else
+		td->td_md.md_spinlock_count++;
 	critical_enter();
 }
 
@@ -505,12 +509,14 @@ void
 spinlock_exit(void)
 {
 	struct thread *td;
+	register_t cspr;
 
 	td = curthread;
 	critical_exit();
+	cspr = td->td_md.md_saved_cspr;
 	td->td_md.md_spinlock_count--;
 	if (td->td_md.md_spinlock_count == 0)
-		restore_interrupts(td->td_md.md_saved_cspr);
+		restore_interrupts(cspr);
 }
 
 /*
diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c
index 4901b38..0fbd519 100644
--- a/sys/i386/i386/machdep.c
+++ b/sys/i386/i386/machdep.c
@@ -2997,11 +2997,15 @@ void
 spinlock_enter(void)
 {
 	struct thread *td;
+	register_t flags;
 
 	td = curthread;
-	if (td->td_md.md_spinlock_count == 0)
-		td->td_md.md_saved_flags = intr_disable();
-	td->td_md.md_spinlock_count++;
+	if (td->td_md.md_spinlock_count == 0) {
+		flags = intr_disable();
+		td->td_md.md_spinlock_count = 1;
+		td->td_md.md_saved_flags = flags;
+	} else
+		td->td_md.md_spinlock_count++;
 	critical_enter();
 }
 
@@ -3009,12 +3013,14 @@ void
 spinlock_exit(void)
 {
 	struct thread *td;
+	register_t flags;
 
 	td = curthread;
 	critical_exit();
+	flags = td->td_md.md_saved_flags;
 	td->td_md.md_spinlock_count--;
 	if (td->td_md.md_spinlock_count == 0)
-		intr_restore(td->td_md.md_saved_flags);
+		intr_restore(flags);
 }
 
 #if defined(I586_CPU) && !defined(NO_F00F_HACK)
diff --git a/sys/ia64/ia64/machdep.c b/sys/ia64/ia64/machdep.c
index ed00a04..119c36f 100644
--- a/sys/ia64/ia64/machdep.c
+++ b/sys/ia64/ia64/machdep.c
@@ -513,11 +513,15 @@ void
 spinlock_enter(void)
 {
 	struct thread *td;
+	int intr;
 
 	td = curthread;
-	if (td->td_md.md_spinlock_count == 0)
-		td->td_md.md_saved_intr = intr_disable();
-	td->td_md.md_spinlock_count++;
+	if (td->td_md.md_spinlock_count == 0) {
+		intr = intr_disable();
+		td->td_md.md_spinlock_count = 1;
+		td->td_md.md_saved_intr = intr;
+	} else
+		td->td_md.md_spinlock_count++;
 	critical_enter();
 }
 
@@ -525,12 +529,14 @@ void
 spinlock_exit(void)
 {
 	struct thread *td;
+	int intr;
 
 	td = curthread;
 	critical_exit();
+	intr = td->td_md.md_saved_intr;
 	td->td_md.md_spinlock_count--;
 	if (td->td_md.md_spinlock_count == 0)
-		intr_restore(td->td_md.md_saved_intr);
+		intr_restore(intr);
 }
 
 void
diff --git a/sys/mips/mips/machdep.c b/sys/mips/mips/machdep.c
index 435b9b4..314bfd1 100644
--- a/sys/mips/mips/machdep.c
+++ b/sys/mips/mips/machdep.c
@@ -450,11 +450,15 @@ void
 spinlock_enter(void)
 {
 	struct thread *td;
+	register_t intr;
 
 	td = curthread;
-	if (td->td_md.md_spinlock_count == 0)
-		td->td_md.md_saved_intr = intr_disable();
-	td->td_md.md_spinlock_count++;
+	if (td->td_md.md_spinlock_count == 0) {
+		intr = intr_disable();
+		td->td_md.md_spinlock_count = 1;
+		td->td_md.md_saved_intr = intr;
+	} else
+		td->td_md.md_spinlock_count++;
 	critical_enter();
 }
 
@@ -462,12 +466,14 @@ void
 spinlock_exit(void)
 {
 	struct thread *td;
+	register_t intr;
 
 	td = curthread;
 	critical_exit();
+	intr = td->td_md.md_saved_intr;
 	td->td_md.md_spinlock_count--;
 	if (td->td_md.md_spinlock_count == 0)
-		intr_restore(td->td_md.md_saved_intr);
+		intr_restore(intr);
 }
 
 /*
diff --git a/sys/pc98/pc98/machdep.c b/sys/pc98/pc98/machdep.c
index e01ef68..942aa45 100644
--- a/sys/pc98/pc98/machdep.c
+++ b/sys/pc98/pc98/machdep.c
@@ -2340,11 +2340,15 @@ void
 spinlock_enter(void)
 {
 	struct thread *td;
+	register_t flags;
 
 	td = curthread;
-	if (td->td_md.md_spinlock_count == 0)
-		td->td_md.md_saved_flags = intr_disable();
-	td->td_md.md_spinlock_count++;
+	if (td->td_md.md_spinlock_count == 0) {
+		flags = intr_disable();
+		td->td_md.md_spinlock_count = 1;
+		td->td_md.md_saved_flags = flags;
+	} else
+		td->td_md.md_spinlock_count++;
 	critical_enter();
 }
 
@@ -2352,12 +2356,14 @@ void
 spinlock_exit(void)
 {
 	struct thread *td;
+	register_t flags;
 
 	td = curthread;
 	critical_exit();
+	flags = td->td_md.md_saved_flags;
 	td->td_md.md_spinlock_count--;
 	if (td->td_md.md_spinlock_count == 0)
-		intr_restore(td->td_md.md_saved_flags);
+		intr_restore(flags);
 }
 
 #if defined(I586_CPU) && !defined(NO_F00F_HACK)
diff --git a/sys/powerpc/aim/machdep.c b/sys/powerpc/aim/machdep.c
index 9dec1f7..0331b50 100644
--- a/sys/powerpc/aim/machdep.c
+++ b/sys/powerpc/aim/machdep.c
@@ -751,11 +751,15 @@ void
 spinlock_enter(void)
 {
 	struct thread *td;
+	register_t msr;
 
 	td = curthread;
-	if (td->td_md.md_spinlock_count == 0)
-		td->td_md.md_saved_msr = intr_disable();
-	td->td_md.md_spinlock_count++;
+	if (td->td_md.md_spinlock_count == 0) {
+		msr = intr_disable();
+		td->td_md.md_spinlock_count = 1;
+		td->td_md.md_saved_msr = msr;
+	} else
+		td->td_md.md_spinlock_count++;
 	critical_enter();
 }
 
@@ -763,12 +767,14 @@ void
 spinlock_exit(void)
 {
 	struct thread *td;
+	register_t msr;
 
 	td = curthread;
 	critical_exit();
+	msr = td->td_md.md_saved_msr;
 	td->td_md.md_spinlock_count--;
 	if (td->td_md.md_spinlock_count == 0)
-		intr_restore(td->td_md.md_saved_msr);
+		intr_restore(msr);
 }
 
 /*
diff --git a/sys/powerpc/booke/machdep.c b/sys/powerpc/booke/machdep.c
index c4b80cc..d216292 100644
--- a/sys/powerpc/booke/machdep.c
+++ b/sys/powerpc/booke/machdep.c
@@ -516,11 +516,15 @@ void
 spinlock_enter(void)
 {
 	struct thread *td;
+	register_t msr;
 
 	td = curthread;
-	if (td->td_md.md_spinlock_count == 0)
-		td->td_md.md_saved_msr = intr_disable();
-	td->td_md.md_spinlock_count++;
+	if (td->td_md.md_spinlock_count == 0) {
+		msr = intr_disable();
+		td->td_md.md_spinlock_count = 1;
+		td->td_md.md_saved_msr = msr;
+	} else
+		td->td_md.md_spinlock_count++;
 	critical_enter();
 }
 
@@ -528,12 +532,14 @@ void
 spinlock_exit(void)
 {
 	struct thread *td;
+	register_t msr;
 
 	td = curthread;
 	critical_exit();
+	msr = td->td_md.md_saved_msr;
 	td->td_md.md_spinlock_count--;
 	if (td->td_md.md_spinlock_count == 0)
-		intr_restore(td->td_md.md_saved_msr);
+		intr_restore(msr);
 }
 
 /* Shutdown the CPU as much as possible. */
diff --git a/sys/sparc64/sparc64/machdep.c b/sys/sparc64/sparc64/machdep.c
index 82643ab..0a40bad 100644
--- a/sys/sparc64/sparc64/machdep.c
+++ b/sys/sparc64/sparc64/machdep.c
@@ -224,9 +224,10 @@ spinlock_enter(void)
 	if (td->td_md.md_spinlock_count == 0) {
 		pil = rdpr(pil);
 		wrpr(pil, 0, PIL_TICK);
+		td->td_md.md_spinlock_count = 1;
 		td->td_md.md_saved_pil = pil;
-	}
-	td->td_md.md_spinlock_count++;
+	} else
+		td->td_md.md_spinlock_count++;
 	critical_enter();
 }
 
@@ -234,12 +235,14 @@ void
 spinlock_exit(void)
 {
 	struct thread *td;
+	register_t pil;
 
 	td = curthread;
 	critical_exit();
+	pil = td->td_md.md_saved_pil;
 	td->td_md.md_spinlock_count--;
 	if (td->td_md.md_spinlock_count == 0)
-		wrpr(pil, td->td_md.md_saved_pil, 0);
+		wrpr(pil, pil, 0);
 }
 
 static phandle_t
diff --git a/sys/sun4v/sun4v/machdep.c b/sys/sun4v/sun4v/machdep.c
index 3a80bee..43496e3 100644
--- a/sys/sun4v/sun4v/machdep.c
+++ b/sys/sun4v/sun4v/machdep.c
@@ -269,9 +269,10 @@ spinlock_enter(void)
 	td = curthread;
 	if (td->td_md.md_spinlock_count == 0) {
 		pil = intr_disable();
+		td->td_md.md_spinlock_count = 1;
 		td->td_md.md_saved_pil = pil;
-	}
-	td->td_md.md_spinlock_count++;
+	} else
+		td->td_md.md_spinlock_count++;
 	critical_enter();
 }
 
@@ -279,14 +280,14 @@ void
 spinlock_exit(void)
 {
 	struct thread *td;
+	register_t pil;
 
 	td = curthread;
 	critical_exit();
+	pil = td->td_md.md_saved_pil;
 	td->td_md.md_spinlock_count--;
-	if (td->td_md.md_spinlock_count == 0) {
-		intr_restore(td->td_md.md_saved_pil);
-	}
-
+	if (td->td_md.md_spinlock_count == 0)
+		intr_restore(pil);
 }
 
 unsigned