diff options
Diffstat (limited to 'kernel/tracepoint.c')
| -rw-r--r-- | kernel/tracepoint.c | 91 |
1 files changed, 59 insertions, 32 deletions
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index 7261fa0f5e3c..9f478d29b926 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -53,6 +53,12 @@ struct tp_probes { struct tracepoint_func probes[]; }; +/* Called in removal of a func but failed to allocate a new tp_funcs */ +static void tp_stub_func(void) +{ + return; +} + static inline void *allocate_probes(int count) { struct tp_probes *p = kmalloc(struct_size(p, probes, count), @@ -130,8 +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 pos = -1; + int iter_probes; /* Iterate over old probe array. */ + int nr_probes = 0; /* Counter for probes */ + int pos = -1; /* Insertion position into new array */ if (WARN_ON(!tp_func->func)) return ERR_PTR(-EINVAL); @@ -140,13 +147,13 @@ 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); + nr_probes++; } } /* + 2 : one for new probe, one for NULL func */ @@ -154,20 +161,24 @@ func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func, if (new == NULL) return ERR_PTR(-ENOMEM); if (old) { - 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)); + 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 */ + } new[pos] = *tp_func; - new[nr_probes + 1].func = NULL; + new[nr_probes].func = NULL; *funcs = new; debug_print_probes(*funcs); return old; @@ -188,8 +199,9 @@ static void *func_remove(struct tracepoint_func **funcs, /* (N -> M), (N > 1, M >= 0) probes */ if (tp_func->func) { for (nr_probes = 0; old[nr_probes].func; nr_probes++) { - if (old[nr_probes].func == tp_func->func && - old[nr_probes].data == tp_func->data) + if ((old[nr_probes].func == tp_func->func && + old[nr_probes].data == tp_func->data) || + old[nr_probes].func == tp_stub_func) nr_del++; } } @@ -208,14 +220,27 @@ static void *func_remove(struct tracepoint_func **funcs, /* N -> M, (N > 1, M > 0) */ /* + 1 for NULL */ new = allocate_probes(nr_probes - nr_del + 1); - if (new == NULL) - return ERR_PTR(-ENOMEM); - for (i = 0; old[i].func; i++) - if (old[i].func != tp_func->func - || old[i].data != tp_func->data) - new[j++] = old[i]; - new[nr_probes - nr_del].func = NULL; - *funcs = new; + 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) + new[j++] = old[i]; + } + new[nr_probes - nr_del].func = NULL; + *funcs = new; + } else { + /* + * Failed to allocate, replace the old function + * with calls to tp_stub_func. + */ + for (i = 0; old[i].func; i++) { + if (old[i].func == tp_func->func && + old[i].data == tp_func->data) + WRITE_ONCE(old[i].func, tp_stub_func); + } + *funcs = old; + } } debug_print_probes(*funcs); return old; @@ -295,10 +320,12 @@ static int tracepoint_remove_func(struct tracepoint *tp, tp_funcs = rcu_dereference_protected(tp->funcs, lockdep_is_held(&tracepoints_mutex)); old = func_remove(&tp_funcs, func); - if (IS_ERR(old)) { - WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM); + if (WARN_ON_ONCE(IS_ERR(old))) return PTR_ERR(old); - } + + if (tp_funcs == old) + /* Failed allocating new tp_funcs, replaced func with stub */ + return 0; if (!tp_funcs) { /* Removed last function */ |