[PATCH 1/1] tracepoint: cleanup: do not fail unregistration

Mathieu Desnoyers
2021-02-03T18:03:52Z

This patch is only compile-tested.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
include/linux/tracepoint.h | 2 +-
kernel/tracepoint.c | 80 +++++++++++++-------------------------
2 files changed, 28 insertions(+), 54 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 0f21617f1a66..fae8d6d9588c 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -308,7 +308,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
it_func_ptr = \
rcu_dereference_raw((&__tracepoint_##_name)->funcs); \
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 3e261482296c..b1bec710f68a 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -136,9 +136,10 @@ 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 = 0; /* Iterate over old probe array. */
+ int nr_old_probes = 0; /* Count non-stub functions in old. */
+ int nr_new_probes = 0; /* Count functions in new. */
+ int pos = -1; /* Insert position in new. */

if (WARN_ON(!tp_func->func))
return ERR_PTR(-EINVAL);
@@ -147,54 +148,34 @@ 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++;
+ /* Insert before probes of lower priority */
+ if (pos < 0 && old[iter_probes].prio < prio)
+ pos = nr_old_probes;
+ nr_old_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_old_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));
+ for (iter_probes = 0; old[iter_probes].func; iter_probes++) {
+ if (old[iter_probes].func == tp_stub_func)
+ continue; /* Skip stub functions. */
+ if (nr_new_probes != pos)
+ new[nr_new_probes] = old[iter_probes];
+ nr_new_probes++;
}
} else
pos = 0;
new[pos] = *tp_func;
- new[nr_probes + 1].func = NULL;
+ new[nr_new_probes + 1].func = NULL;
*funcs = new;
debug_print_probes(*funcs);
return old;
@@ -238,9 +219,9 @@ static void *func_remove(struct tracepoint_func **funcs,
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)
+ 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;
@@ -251,15 +232,8 @@ static void *func_remove(struct tracepoint_func **funcs,
*/
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);
*funcs = old;
}
}
--
2.20.1