path: root/arch
diff options
authorLorenzo Pieralisi <>2015-11-17 11:50:51 +0000
committerCatalin Marinas <>2015-11-17 17:11:45 +0000
commitde818bd4522c40ea02a81b387d2fa86f989c9623 (patch)
treea52307d97ef63e2ba241531f4c7d5ab030243fb6 /arch
parentadc235aff6fcf5ae4d8dc00faf30a07632b9725b (diff)
arm64: kernel: pause/unpause function graph tracer in cpu_suspend()
The function graph tracer adds instrumentation that is required to trace both entry and exit of a function. In particular the function graph tracer updates the "return address" of a function in order to insert a trace callback on function exit. Kernel power management functions like cpu_suspend() are called upon power down entry with functions called "finishers" that are in turn called to trigger the power down sequence but they may not return to the kernel through the normal return path. When the core resumes from low-power it returns to the cpu_suspend() function through the cpu_resume path, which leaves the trace stack frame set-up by the function tracer in an incosistent state upon return to the kernel when tracing is enabled. This patch fixes the issue by pausing/resuming the function graph tracer on the thread executing cpu_suspend() (ie the function call that subsequently triggers the "suspend finishers"), so that the function graph tracer state is kept consistent across functions that enter power down states and never return by effectively disabling graph tracer while they are executing. Fixes: 819e50e25d0c ("arm64: Add ftrace support") Signed-off-by: Lorenzo Pieralisi <> Reported-by: Catalin Marinas <> Reported-by: AKASHI Takahiro <> Suggested-by: Steven Rostedt <> Acked-by: Steven Rostedt <> Cc: Will Deacon <> Cc: <> # 3.16+ Signed-off-by: Catalin Marinas <>
Diffstat (limited to 'arch')
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
index fce95e17cf7f..1095aa483a1c 100644
--- a/arch/arm64/kernel/suspend.c
+++ b/arch/arm64/kernel/suspend.c
@@ -1,3 +1,4 @@
+#include <linux/ftrace.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <asm/cacheflush.h>
@@ -71,6 +72,13 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
+ * Function graph tracer state gets incosistent when the kernel
+ * calls functions that never return (aka suspend finishers) hence
+ * disable graph tracing during their execution.
+ */
+ pause_graph_tracing();
+ /*
* mm context saved on the stack, it will be restored when
* the cpu comes out of reset through the identity mapped
* page tables, so that the thread address space is properly
@@ -111,6 +119,8 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
+ unpause_graph_tracing();
* Restore pstate flags. OS lock and mdscr have been already
* restored, so from this point onwards, debugging is fully