----- On Feb 4, 2021, at 1:27 PM, rostedt rost...@goodmis.org wrote: > From: "Steven Rostedt (VMware)" <rost...@goodmis.org> > > Restructure the code a bit to make it simpler, fix some formatting problems > and add READ_ONCE/WRITE_ONCE to make sure there's no compiler tear downs on
compiler tear downs -> compiler load/store tearing. > changes to variables that can be accessed across CPUs. > > Started with Mathieu Desnoyers's patch: > > Link: > > https://lore.kernel.org/lkml/20210203175741.20665-1-mathieu.desnoy...@efficios.com/ > > And will keep his signature, but I will take the responsibility of this > being correct, and keep the authorship. > > Signed-off-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com> > Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org> > --- > include/linux/tracepoint.h | 2 +- > kernel/tracepoint.c | 92 +++++++++++++++----------------------- > 2 files changed, 37 insertions(+), 57 deletions(-) > > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h > index 966ed8980327..dc1d4c612cc3 100644 > --- a/include/linux/tracepoint.h > +++ b/include/linux/tracepoint.h > @@ -309,7 +309,7 @@ static inline struct tracepoint > *tracepoint_ptr_deref(tracepoint_ptr_t *p) > rcu_dereference_raw((&__tracepoint_##_name)->funcs); \ > if (it_func_ptr) { \ > do { \ > - it_func = (it_func_ptr)->func; \ > + it_func = READ_ONCE((it_func_ptr)->func); \ > __data = (it_func_ptr)->data; \ > ((void(*)(void *, proto))(it_func))(__data, > args); \ > } while ((++it_func_ptr)->func); \ > diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c > index e8f20ae29c18..4b9de79bb927 100644 > --- a/kernel/tracepoint.c > +++ b/kernel/tracepoint.c > @@ -136,9 +136,9 @@ func_add(struct tracepoint_func **funcs, struct > tracepoint_func *tp_func, > int prio) > { > struct tracepoint_func *old, *new; > - int nr_probes = 0; > - int stub_funcs = 0; > - int pos = -1; > + int iter_probes; /* Iterate over old probe array. */ > + int nr_probes = 0; /* Counter for probes */ > + int pos = -1; /* New position */ New position -> Insertion position into new array > > if (WARN_ON(!tp_func->func)) > return ERR_PTR(-EINVAL); > @@ -147,54 +147,39 @@ func_add(struct tracepoint_func **funcs, struct > tracepoint_func *tp_func, > old = *funcs; > if (old) { > /* (N -> N+1), (N != 0, 1) probes */ > - for (nr_probes = 0; old[nr_probes].func; nr_probes++) { > - /* Insert before probes of lower priority */ > - if (pos < 0 && old[nr_probes].prio < prio) > - pos = nr_probes; > - if (old[nr_probes].func == tp_func->func && > - old[nr_probes].data == tp_func->data) > + for (iter_probes = 0; old[iter_probes].func; iter_probes++) { > + if (old[iter_probes].func == tp_stub_func) > + continue; /* Skip stub functions. */ > + if (old[iter_probes].func == tp_func->func && > + old[iter_probes].data == tp_func->data) > return ERR_PTR(-EEXIST); > - if (old[nr_probes].func == tp_stub_func) > - stub_funcs++; > + nr_probes++; > } > } > - /* + 2 : one for new probe, one for NULL func - stub functions */ > - new = allocate_probes(nr_probes + 2 - stub_funcs); > + /* + 2 : one for new probe, one for NULL func */ > + new = allocate_probes(nr_probes + 2); > if (new == NULL) > return ERR_PTR(-ENOMEM); > if (old) { > - if (stub_funcs) { > - /* Need to copy one at a time to remove stubs */ > - int probes = 0; > - > - pos = -1; > - for (nr_probes = 0; old[nr_probes].func; nr_probes++) { > - if (old[nr_probes].func == tp_stub_func) > - continue; > - if (pos < 0 && old[nr_probes].prio < prio) > - pos = probes++; > - new[probes++] = old[nr_probes]; > - } > - nr_probes = probes; > - if (pos < 0) > - pos = probes; > - else > - nr_probes--; /* Account for insertion */ > - > - } else if (pos < 0) { > - pos = nr_probes; > - memcpy(new, old, nr_probes * sizeof(struct > tracepoint_func)); > - } else { > - /* Copy higher priority probes ahead of the new probe */ > - memcpy(new, old, pos * sizeof(struct tracepoint_func)); > - /* Copy the rest after it. */ > - memcpy(new + pos + 1, old + pos, > - (nr_probes - pos) * sizeof(struct > tracepoint_func)); > + pos = -1; pos is already initialized to -1 at function beginning. > + nr_probes = 0; > + for (iter_probes = 0; old[iter_probes].func; iter_probes++) { > + if (old[iter_probes].func == tp_stub_func) > + continue; > + /* Insert before probes of lower priority */ > + if (pos < 0 && old[iter_probes].prio < prio) > + pos = nr_probes++; > + new[nr_probes++] = old[iter_probes]; > } > - } else > + if (pos < 0) > + pos = nr_probes++; > + /* nr_probes now points to the end of the new array */ > + } else { > pos = 0; > + nr_probes = 1; /* must point at end of array */ Yep, much nicer. > + } > new[pos] = *tp_func; > - new[nr_probes + 1].func = NULL; > + new[nr_probes].func = NULL; > *funcs = new; > debug_print_probes(*funcs); > return old; > @@ -237,11 +222,12 @@ static void *func_remove(struct tracepoint_func **funcs, > /* + 1 for NULL */ > new = allocate_probes(nr_probes - nr_del + 1); > if (new) { > - for (i = 0; old[i].func; i++) > - if ((old[i].func != tp_func->func > - || old[i].data != tp_func->data) > - && old[i].func != tp_stub_func) > + for (i = 0; old[i].func; i++) { > + if ((old[i].func != tp_func->func || > + old[i].data != tp_func->data) && > + old[i].func != tp_stub_func) > new[j++] = old[i]; > + } > new[nr_probes - nr_del].func = NULL; > *funcs = new; > } else { > @@ -249,17 +235,11 @@ static void *func_remove(struct tracepoint_func **funcs, > * Failed to allocate, replace the old function > * with calls to tp_stub_func. > */ > - for (i = 0; old[i].func; i++) > + for (i = 0; old[i].func; i++) { > if (old[i].func == tp_func->func && > - old[i].data == tp_func->data) { > - old[i].func = tp_stub_func; > - /* Set the prio to the next event. */ > - if (old[i + 1].func) > - old[i].prio = > - old[i + 1].prio; > - else > - old[i].prio = -1; > - } > + old[i].data == tp_func->data) > + WRITE_ONCE(old[i].func, tp_stub_func); > + } The rest looks good, thanks! You can keep my signed-off-by, and if needed may add my reviewed-by tag as well. ;-) Mathieu > *funcs = old; > } > } > -- > 2.25.4 -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
