@@ -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))
local_dbg_save(flags);
/*
+ * 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))
hw_breakpoint_restore(NULL);
}
+ unpause_graph_tracing();
+
/*
* Restore pstate flags. OS lock and mdscr have been already
* restored, so from this point onwards, debugging is fully
This is a note to let you know that I have just added a patch titled arm64: kernel: pause/unpause function graph tracer in cpu_suspend() to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue This patch is scheduled to be released in version 4.2.8-ckt2. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 4.2.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ---8<------------------------------------------------------------ From 3198d56c7b4db3401d9aa7edc7795afc8746b663 Mon Sep 17 00:00:00 2001 From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Date: Tue, 17 Nov 2015 11:50:51 +0000 Subject: arm64: kernel: pause/unpause function graph tracer in cpu_suspend() commit de818bd4522c40ea02a81b387d2fa86f989c9623 upstream. 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 <lorenzo.pieralisi@arm.com> Reported-by: Catalin Marinas <catalin.marinas@arm.com> Reported-by: AKASHI Takahiro <takahiro.akashi@linaro.org> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- arch/arm64/kernel/suspend.c | 10 ++++++++++ 1 file changed, 10 insertions(+) -- 1.9.1