Re: [PATCH 0/7] IO CPU affinity testing series

[Alan D. Brunelle]

Subject: [PATCH] Fixed race: using potentially invalid pointer

When data->flags & CSD_FLAG_ALLOC is true, the data could be freed by the other processor before we check for CSD_FLAG_WAIT.

Also: removed old comment, doesn't quite fit anymore.

This is applied against Jens' git tree w/ the ia64 additional commit.

Signed-off-by: Alan D. Brunelle <alan.brunelle@xxxxxx>
---
 arch/ia64/kernel/smp.c   |    5 ++---
 arch/x86/kernel/smp_32.c |    5 ++---
 arch/x86/kernel/smp_64.c |    5 ++---
 3 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/arch/ia64/kernel/smp.c b/arch/ia64/kernel/smp.c
index 521bc52..ad153e2 100644
--- a/arch/ia64/kernel/smp.c
+++ b/arch/ia64/kernel/smp.c
@@ -407,8 +407,7 @@ void __smp_call_function_single(int cpu, struct call_single_data *data)
 {
 	struct call_single_queue *dst;
 	unsigned long flags;
-	/* prevent preemption and reschedule on another processor */
-	int ipi;
+	int ipi, wait_done = data->flags & CSD_FLAG_WAIT;
 
 	/* Can deadlock when called with interrupts disabled */
 	WARN_ON((data->flags & CSD_FLAG_WAIT) && irqs_disabled());
@@ -424,7 +423,7 @@ void __smp_call_function_single(int cpu, struct call_single_data *data)
 	if (ipi)
 		send_IPI_single(cpu, IPI_CALL_FUNC_SINGLE);
 
-	if (data->flags & CSD_FLAG_WAIT) {
+	if (wait_done) {
 		/* Wait for response */
 		while (data->flags)
 			cpu_relax();
diff --git a/arch/x86/kernel/smp_32.c b/arch/x86/kernel/smp_32.c
index dcbb89c..8239814 100644
--- a/arch/x86/kernel/smp_32.c
+++ b/arch/x86/kernel/smp_32.c
@@ -638,8 +638,7 @@ void __smp_call_function_single(int cpu, struct call_single_data *data)
 	cpumask_t mask = cpumask_of_cpu(cpu);
 	struct call_single_queue *dst;
 	unsigned long flags;
-	/* prevent preemption and reschedule on another processor */
-	int ipi;
+	int ipi, wait_done = data->flags & CSD_FLAG_WAIT;
 
 	/* Can deadlock when called with interrupts disabled */
 	WARN_ON((data->flags & CSD_FLAG_WAIT) && irqs_disabled());
@@ -655,7 +654,7 @@ void __smp_call_function_single(int cpu, struct call_single_data *data)
 	if (ipi)
 		send_IPI_mask(mask, CALL_FUNCTION_SINGLE_VECTOR);
 
-	if (data->flags & CSD_FLAG_WAIT) {
+	if (wait_done) {
 		/* Wait for response */
 		while (data->flags)
 			cpu_relax();
diff --git a/arch/x86/kernel/smp_64.c b/arch/x86/kernel/smp_64.c
index 7e4e300..c89a4f7 100644
--- a/arch/x86/kernel/smp_64.c
+++ b/arch/x86/kernel/smp_64.c
@@ -458,8 +458,7 @@ void __smp_call_function_single(int cpu, struct call_single_data *data)
 	cpumask_t mask = cpumask_of_cpu(cpu);
 	struct call_single_queue *dst;
 	unsigned long flags;
-	/* prevent preemption and reschedule on another processor */
-	int ipi;
+	int ipi, wait_done = data->flags & CSD_FLAG_WAIT;
 
 	/* Can deadlock when called with interrupts disabled */
 	WARN_ON((data->flags & CSD_FLAG_WAIT) && irqs_disabled());
@@ -475,7 +474,7 @@ void __smp_call_function_single(int cpu, struct call_single_data *data)
 	if (ipi)
 		send_IPI_mask(mask, CALL_FUNCTION_SINGLE_VECTOR);
 
-	if (data->flags & CSD_FLAG_WAIT) {
+	if (wait_done) {
 		/* Wait for response */
 		while (data->flags)
 			cpu_relax();
-- 
1.5.2.5

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