The behaviour of the thread_change_pc() function is a bit cryptic
without being more familiar with how the watchpoint logic handles
perf's after-execute semantics.
Expand the comment to explain why we can re-insert the breakpoint and
unset the perf_single_step flag.
Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230801011744.153973-2-bgray@linux.ibm.com
* Restores the breakpoint on the debug registers.
* Invoke this function if it is known that the execution context is
* about to change to cause loss of MSR_SE settings.
+ *
+ * The perf watchpoint will simply re-trigger once the thread is started again,
+ * and the watchpoint handler will set up MSR_SE and perf_single_step as
+ * needed.
*/
void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs)
{