Kevin Hilman khilman@linaro.org writes:
commit 91d1aa43 (context_tracking: New context tracking susbsystem) generalized parts of the RCU userspace extended quiescent state into the context tracking subsystem. Context tracking is then used to implement adaptive tickless (a.k.a extended nohz)
To support the new context tracking subsystem on ARM, the user/kernel boundary transtions need to be instrumented.
For exceptions and IRQs in usermode, the existing usr_entry macro is used to instrument the user->kernel transition. For the return to usermode path, the ret_to_user* path is instrumented. Using the usr_entry macro, this covers interrupts in userspace, data abort and prefetch abort exceptions in userspace as well as undefined exceptions in userspace (which is where FP emulation and VFP are handled.)
For syscalls, the slow return path is covered by instrumenting the ret_to_user path. In addition, the syscall entry point is instrumented which covers the user->kernel transition for both fast and slow syscalls, and an additional instrumentation point is added for the fast syscall return path (ret_fast_syscall).
Cc: Mats Liljegren mats.liljegren@enea.com Cc: Frederic Weisbecker fweisbec@gmail.com Signed-off-by: Kevin Hilman khilman@linaro.org
This version has been submitted to Russell's patch tracker as patch 7688[1] after making the minor change below.
[...]
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 0f82098..3449d30 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -396,6 +396,7 @@ ENDPROC(__pabt_svc) #ifdef CONFIG_IRQSOFF_TRACER bl trace_hardirqs_off #endif
- ct_user_exit, save = 0 .endm
Removed the ',' after the macro here an elsewhere.
It's harmless, but not needed and removing it makes this look like other macro usage throughout.
Kevin
[1] http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=7688/1