On Tue, 26 Apr 2016, Balbir Singh wrote: > > + + Anything inlined into __schedule() can not be patched. > > + > > + The switch_to macro is inlined into __schedule(). It switches the > > + context between two processes in the middle of the macro. It does > > + not save RIP in x86_64 version (contrary to 32-bit version). Instead, > > + the currently used __schedule()/switch_to() handles both processes. > > + > > + Now, let's have two different tasks. One calls the original > > + __schedule(), its registers are stored in a defined order and it > > + goes to sleep in the switch_to macro and some other task is restored > > + using the original __schedule(). Then there is the second task which > > + calls patched__schedule(), it goes to sleep there and the first task > > + is picked by the patched__schedule(). Its RSP is restored and now > > + the registers should be restored as well. But the order is different > > + in the new patched__schedule(), so... > > + > > + There is a work in progress to remove this limitation. > > + > > I am afraid the example requires more clarification. I don't quite get the order is different Different order is not inevitable but perfectly possible (even probable). GCC may simply generate different object code for patched__schedule() than it did for __schedule(). The problem is when the prologue and epilogue are different. Miroslav -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
