On Thu, 21 Apr 2022 19:36:06 +0800 patrick wang <patrick.wang.shcn@xxxxxxxxx> wrote: > On Thu, Apr 21, 2022 at 12:26 AM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > > > On Wed, 20 Apr 2022 11:44:54 -0400 > > Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > > > > > Interesting. On x86 when we used stop machine[*] it was not an issue to > > modify the code that is being executed in stop machine. I'm curious to > > exactly what the issue is if something does get traced in the stop machine > > processing. Why does it crash? > > I looked up the commit history. When x86 turned to breakpoints, stop > machine's state machine loop had no calls during waiting. So there > was no function being called during modifying code. Which means > there were no other cpus would load those instructions to be updated > in this period. While the stop machine currently will call other functions > and the call chain is fairly deep. So it may not quite be suitable for ftrace > now because it can not make sure the instructions within its own call > chain are updated atomically. Are you saying that the RISC-V stop machine implementation has code being called on the other CPUs while they wait? -- Steve
