Hi Greg, On Tue, Jan 26, 2016 at 10:54:50PM -0800, gregkh@xxxxxxxxxxxxxxxxxxx wrote: > > This is a note to let you know that I've just added the patch titled > > arm64: kernel: pause/unpause function graph tracer in cpu_suspend() > > to the 4.1-stable tree which can be found at: > http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary > > The filename of the patch is: > arm64-kernel-pause-unpause-function-graph-tracer-in-cpu_suspend.patch > and it can be found in the queue-4.1 subdirectory. > > If you, or anyone else, feels it should not be added to the stable tree, > please let <stable@xxxxxxxxxxxxxxx> know about it. We have just noticed this patch did not make it to 3.18 stable kernel even though it was marked for #3.16+, probably it has slipped through the cracks, please let us know what we can do to get it applied to the 3.18 stable tree. Thanks ! Lorenzo > > > From de818bd4522c40ea02a81b387d2fa86f989c9623 Mon Sep 17 00:00:00 2001 > From: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> > Date: Tue, 17 Nov 2015 11:50:51 +0000 > Subject: arm64: kernel: pause/unpause function graph tracer in cpu_suspend() > > From: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> > > 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@xxxxxxx> > Reported-by: Catalin Marinas <catalin.marinas@xxxxxxx> > Reported-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx> > Suggested-by: Steven Rostedt <rostedt@xxxxxxxxxxx> > Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx> > Cc: Will Deacon <will.deacon@xxxxxxx> > Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > --- > arch/arm64/kernel/suspend.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > --- 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 ( > 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 ( > 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 > > > Patches currently in stable-queue which might be from lorenzo.pieralisi@xxxxxxx are > > queue-4.1/arm64-kernel-pause-unpause-function-graph-tracer-in-cpu_suspend.patch > -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html