From c89504a703fb779052213add0e8ed642f4a4f1c8 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Fri, 1 Aug 2025 16:37:23 -0400 Subject: [PATCH 1/6] tracing: Remove unneeded goto out logic Several places in the trace.c file there's a goto out where the out is simply a return. There's no reason to jump to the out label if it's not doing any more logic but simply returning from the function. Replace the goto outs with a return and remove the out labels. Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Link: https://lore.kernel.org/20250801203857.538726745@kernel.org Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace.c | 38 +++++++++++++++----------------------- 1 file changed, 15 insertions(+), 23 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 945a8ecf2c62..0ec9cab9a812 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1841,7 +1841,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, ret = get_user(ch, ubuf++); if (ret) - goto out; + return ret; read++; cnt--; @@ -1855,7 +1855,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, while (cnt && isspace(ch)) { ret = get_user(ch, ubuf++); if (ret) - goto out; + return ret; read++; cnt--; } @@ -1865,8 +1865,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, /* only spaces were written */ if (isspace(ch) || !ch) { *ppos += read; - ret = read; - goto out; + return read; } } @@ -1874,13 +1873,12 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, while (cnt && !isspace(ch) && ch) { if (parser->idx < parser->size - 1) parser->buffer[parser->idx++] = ch; - else { - ret = -EINVAL; - goto out; - } + else + return -EINVAL; + ret = get_user(ch, ubuf++); if (ret) - goto out; + return ret; read++; cnt--; } @@ -1895,15 +1893,11 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, /* Make sure the parsed string always terminates with '\0'. */ parser->buffer[parser->idx] = 0; } else { - ret = -EINVAL; - goto out; + return -EINVAL; } *ppos += read; - ret = read; - -out: - return ret; + return read; } /* TODO add a seq_buf_to_buffer() */ @@ -2405,10 +2399,10 @@ int __init register_tracer(struct tracer *type) mutex_unlock(&trace_types_lock); if (ret || !default_bootup_tracer) - goto out_unlock; + return ret; if (strncmp(default_bootup_tracer, type->name, MAX_TRACER_SIZE)) - goto out_unlock; + return 0; printk(KERN_INFO "Starting tracer '%s'\n", type->name); /* Do we want this tracer to start on bootup? */ @@ -2420,8 +2414,7 @@ int __init register_tracer(struct tracer *type) /* disable other selftests, since this will break it. */ disable_tracing_selftest("running a tracer"); - out_unlock: - return ret; + return 0; } static void tracing_reset_cpu(struct array_buffer *buf, int cpu) @@ -8963,12 +8956,12 @@ ftrace_trace_snapshot_callback(struct trace_array *tr, struct ftrace_hash *hash, out_reg: ret = tracing_arm_snapshot(tr); if (ret < 0) - goto out; + return ret; ret = register_ftrace_function_probe(glob, tr, ops, count); if (ret < 0) tracing_disarm_snapshot(tr); - out: + return ret < 0 ? ret : 0; } @@ -11070,7 +11063,7 @@ __init static int tracer_alloc_buffers(void) BUILD_BUG_ON(TRACE_ITER_LAST_BIT > TRACE_FLAGS_MAX_SIZE); if (!alloc_cpumask_var(&tracing_buffer_mask, GFP_KERNEL)) - goto out; + return -ENOMEM; if (!alloc_cpumask_var(&global_trace.tracing_cpumask, GFP_KERNEL)) goto out_free_buffer_mask; @@ -11188,7 +11181,6 @@ out_free_cpumask: free_cpumask_var(global_trace.tracing_cpumask); out_free_buffer_mask: free_cpumask_var(tracing_buffer_mask); -out: return ret; } From 788fa4b47cdcd9b3d8c2d02ac0b3cd2540305f18 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Fri, 1 Aug 2025 16:37:24 -0400 Subject: [PATCH 2/6] tracing: Add guard(ring_buffer_nest) Some calls to the tracing ring buffer can happen when the ring buffer is already being written to by the same context (for example, a trace_printk() in between a ring_buffer_lock_reserve() and a ring_buffer_unlock_commit()). In order to not trigger the recursion detection, these functions use ring_buffer_nest_start() and ring_buffer_nest_end(). Create a guard() for these functions so that their use cases can be simplified and not need to use goto for the release. Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Link: https://lore.kernel.org/20250801203857.710501021@kernel.org Signed-off-by: Steven Rostedt (Google) --- include/linux/ring_buffer.h | 3 ++ kernel/trace/trace.c | 69 +++++++++++++------------------ kernel/trace/trace_events_synth.c | 6 +-- 3 files changed, 34 insertions(+), 44 deletions(-) diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index cd7f0ae26615..8253cb69540c 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -144,6 +144,9 @@ int ring_buffer_write(struct trace_buffer *buffer, void ring_buffer_nest_start(struct trace_buffer *buffer); void ring_buffer_nest_end(struct trace_buffer *buffer); +DEFINE_GUARD(ring_buffer_nest, struct trace_buffer *, + ring_buffer_nest_start(_T), ring_buffer_nest_end(_T)) + struct ring_buffer_event * ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts, unsigned long *lost_events); diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 0ec9cab9a812..332487179e1d 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1160,13 +1160,11 @@ int __trace_array_puts(struct trace_array *tr, unsigned long ip, trace_ctx = tracing_gen_ctx(); buffer = tr->array_buffer.buffer; - ring_buffer_nest_start(buffer); + guard(ring_buffer_nest)(buffer); event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, alloc, trace_ctx); - if (!event) { - size = 0; - goto out; - } + if (!event) + return 0; entry = ring_buffer_event_data(event); entry->ip = ip; @@ -1182,8 +1180,6 @@ int __trace_array_puts(struct trace_array *tr, unsigned long ip, __buffer_unlock_commit(buffer, event); ftrace_trace_stack(tr, buffer, trace_ctx, 4, NULL); - out: - ring_buffer_nest_end(buffer); return size; } EXPORT_SYMBOL_GPL(__trace_array_puts); @@ -1213,7 +1209,6 @@ int __trace_bputs(unsigned long ip, const char *str) struct bputs_entry *entry; unsigned int trace_ctx; int size = sizeof(struct bputs_entry); - int ret = 0; if (!printk_binsafe(tr)) return __trace_puts(ip, str, strlen(str)); @@ -1227,11 +1222,11 @@ int __trace_bputs(unsigned long ip, const char *str) trace_ctx = tracing_gen_ctx(); buffer = tr->array_buffer.buffer; - ring_buffer_nest_start(buffer); + guard(ring_buffer_nest)(buffer); event = __trace_buffer_lock_reserve(buffer, TRACE_BPUTS, size, trace_ctx); if (!event) - goto out; + return 0; entry = ring_buffer_event_data(event); entry->ip = ip; @@ -1240,10 +1235,7 @@ int __trace_bputs(unsigned long ip, const char *str) __buffer_unlock_commit(buffer, event); ftrace_trace_stack(tr, buffer, trace_ctx, 4, NULL); - ret = 1; - out: - ring_buffer_nest_end(buffer); - return ret; + return 1; } EXPORT_SYMBOL_GPL(__trace_bputs); @@ -3397,21 +3389,19 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args) size = sizeof(*entry) + sizeof(u32) * len; buffer = tr->array_buffer.buffer; - ring_buffer_nest_start(buffer); - event = __trace_buffer_lock_reserve(buffer, TRACE_BPRINT, size, - trace_ctx); - if (!event) - goto out; - entry = ring_buffer_event_data(event); - entry->ip = ip; - entry->fmt = fmt; + scoped_guard(ring_buffer_nest, buffer) { + event = __trace_buffer_lock_reserve(buffer, TRACE_BPRINT, size, + trace_ctx); + if (!event) + goto out_put; + entry = ring_buffer_event_data(event); + entry->ip = ip; + entry->fmt = fmt; - memcpy(entry->buf, tbuffer, sizeof(u32) * len); - __buffer_unlock_commit(buffer, event); - ftrace_trace_stack(tr, buffer, trace_ctx, 6, NULL); - -out: - ring_buffer_nest_end(buffer); + memcpy(entry->buf, tbuffer, sizeof(u32) * len); + __buffer_unlock_commit(buffer, event); + ftrace_trace_stack(tr, buffer, trace_ctx, 6, NULL); + } out_put: put_trace_buf(); @@ -3452,20 +3442,19 @@ int __trace_array_vprintk(struct trace_buffer *buffer, len = vscnprintf(tbuffer, TRACE_BUF_SIZE, fmt, args); size = sizeof(*entry) + len + 1; - ring_buffer_nest_start(buffer); - event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, size, - trace_ctx); - if (!event) - goto out; - entry = ring_buffer_event_data(event); - entry->ip = ip; - - memcpy(&entry->buf, tbuffer, len + 1); - __buffer_unlock_commit(buffer, event); - ftrace_trace_stack(printk_trace, buffer, trace_ctx, 6, NULL); + scoped_guard(ring_buffer_nest, buffer) { + event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, size, + trace_ctx); + if (!event) + goto out; + entry = ring_buffer_event_data(event); + entry->ip = ip; + memcpy(&entry->buf, tbuffer, len + 1); + __buffer_unlock_commit(buffer, event); + ftrace_trace_stack(printk_trace, buffer, trace_ctx, 6, NULL); + } out: - ring_buffer_nest_end(buffer); put_trace_buf(); out_nobuffer: diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c index 33cfbd4ed76d..f24ee61f8884 100644 --- a/kernel/trace/trace_events_synth.c +++ b/kernel/trace/trace_events_synth.c @@ -536,12 +536,12 @@ static notrace void trace_event_raw_event_synth(void *__data, * is being performed within another event. */ buffer = trace_file->tr->array_buffer.buffer; - ring_buffer_nest_start(buffer); + guard(ring_buffer_nest)(buffer); entry = trace_event_buffer_reserve(&fbuffer, trace_file, sizeof(*entry) + fields_size); if (!entry) - goto out; + return; for (i = 0, n_u64 = 0; i < event->n_fields; i++) { val_idx = var_ref_idx[i]; @@ -584,8 +584,6 @@ static notrace void trace_event_raw_event_synth(void *__data, } trace_event_buffer_commit(&fbuffer); -out: - ring_buffer_nest_end(buffer); } static void free_synth_event_print_fmt(struct trace_event_call *call) From debe57fbe12cb16881b2db1f1787eb9673a8b8b0 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Fri, 1 Aug 2025 16:37:25 -0400 Subject: [PATCH 3/6] tracing: Add guard() around locks and mutexes in trace.c There's several locations in trace.c that can be simplified by using guards around raw_spin_lock_irqsave, mutexes and preempt disabling. Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Link: https://lore.kernel.org/20250801203857.879085376@kernel.org Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace.c | 144 ++++++++++++++----------------------------- 1 file changed, 46 insertions(+), 98 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 332487179e1d..4299e89ed04e 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -432,15 +432,13 @@ static void ftrace_exports(struct ring_buffer_event *event, int flag) { struct trace_export *export; - preempt_disable_notrace(); + guard(preempt_notrace)(); export = rcu_dereference_raw_check(ftrace_exports_list); while (export) { trace_process_export(export, event, flag); export = rcu_dereference_raw_check(export->next); } - - preempt_enable_notrace(); } static inline void @@ -497,27 +495,18 @@ int register_ftrace_export(struct trace_export *export) if (WARN_ON_ONCE(!export->write)) return -1; - mutex_lock(&ftrace_export_lock); + guard(mutex)(&ftrace_export_lock); add_ftrace_export(&ftrace_exports_list, export); - mutex_unlock(&ftrace_export_lock); - return 0; } EXPORT_SYMBOL_GPL(register_ftrace_export); int unregister_ftrace_export(struct trace_export *export) { - int ret; - - mutex_lock(&ftrace_export_lock); - - ret = rm_ftrace_export(&ftrace_exports_list, export); - - mutex_unlock(&ftrace_export_lock); - - return ret; + guard(mutex)(&ftrace_export_lock); + return rm_ftrace_export(&ftrace_exports_list, export); } EXPORT_SYMBOL_GPL(unregister_ftrace_export); @@ -640,9 +629,8 @@ void trace_array_put(struct trace_array *this_tr) if (!this_tr) return; - mutex_lock(&trace_types_lock); + guard(mutex)(&trace_types_lock); __trace_array_put(this_tr); - mutex_unlock(&trace_types_lock); } EXPORT_SYMBOL_GPL(trace_array_put); @@ -1424,13 +1412,8 @@ static int tracing_arm_snapshot_locked(struct trace_array *tr) int tracing_arm_snapshot(struct trace_array *tr) { - int ret; - - mutex_lock(&trace_types_lock); - ret = tracing_arm_snapshot_locked(tr); - mutex_unlock(&trace_types_lock); - - return ret; + guard(mutex)(&trace_types_lock); + return tracing_arm_snapshot_locked(tr); } void tracing_disarm_snapshot(struct trace_array *tr) @@ -2483,9 +2466,8 @@ void tracing_reset_all_online_cpus_unlocked(void) void tracing_reset_all_online_cpus(void) { - mutex_lock(&trace_types_lock); + guard(mutex)(&trace_types_lock); tracing_reset_all_online_cpus_unlocked(); - mutex_unlock(&trace_types_lock); } int is_tracing_stopped(void) @@ -2496,18 +2478,17 @@ int is_tracing_stopped(void) static void tracing_start_tr(struct trace_array *tr) { struct trace_buffer *buffer; - unsigned long flags; if (tracing_disabled) return; - raw_spin_lock_irqsave(&tr->start_lock, flags); + guard(raw_spinlock_irqsave)(&tr->start_lock); if (--tr->stop_count) { if (WARN_ON_ONCE(tr->stop_count < 0)) { /* Someone screwed up their debugging */ tr->stop_count = 0; } - goto out; + return; } /* Prevent the buffers from switching */ @@ -2524,9 +2505,6 @@ static void tracing_start_tr(struct trace_array *tr) #endif arch_spin_unlock(&tr->max_lock); - - out: - raw_spin_unlock_irqrestore(&tr->start_lock, flags); } /** @@ -2544,11 +2522,10 @@ void tracing_start(void) static void tracing_stop_tr(struct trace_array *tr) { struct trace_buffer *buffer; - unsigned long flags; - raw_spin_lock_irqsave(&tr->start_lock, flags); + guard(raw_spinlock_irqsave)(&tr->start_lock); if (tr->stop_count++) - goto out; + return; /* Prevent the buffers from switching */ arch_spin_lock(&tr->max_lock); @@ -2564,9 +2541,6 @@ static void tracing_stop_tr(struct trace_array *tr) #endif arch_spin_unlock(&tr->max_lock); - - out: - raw_spin_unlock_irqrestore(&tr->start_lock, flags); } /** @@ -2679,12 +2653,12 @@ void trace_buffered_event_enable(void) per_cpu(trace_buffered_event, cpu) = event; - preempt_disable(); - if (cpu == smp_processor_id() && - __this_cpu_read(trace_buffered_event) != - per_cpu(trace_buffered_event, cpu)) - WARN_ON_ONCE(1); - preempt_enable(); + scoped_guard(preempt,) { + if (cpu == smp_processor_id() && + __this_cpu_read(trace_buffered_event) != + per_cpu(trace_buffered_event, cpu)) + WARN_ON_ONCE(1); + } } } @@ -3029,7 +3003,7 @@ static void __ftrace_trace_stack(struct trace_array *tr, skip++; #endif - preempt_disable_notrace(); + guard(preempt_notrace)(); stackidx = __this_cpu_inc_return(ftrace_stack_reserve) - 1; @@ -3087,8 +3061,6 @@ static void __ftrace_trace_stack(struct trace_array *tr, /* Again, don't let gcc optimize things here */ barrier(); __this_cpu_dec(ftrace_stack_reserve); - preempt_enable_notrace(); - } static inline void ftrace_trace_stack(struct trace_array *tr, @@ -3171,9 +3143,9 @@ ftrace_trace_userstack(struct trace_array *tr, * prevent recursion, since the user stack tracing may * trigger other kernel events. */ - preempt_disable(); + guard(preempt)(); if (__this_cpu_read(user_stack_count)) - goto out; + return; __this_cpu_inc(user_stack_count); @@ -3191,8 +3163,6 @@ ftrace_trace_userstack(struct trace_array *tr, out_drop_count: __this_cpu_dec(user_stack_count); - out: - preempt_enable(); } #else /* CONFIG_USER_STACKTRACE_SUPPORT */ static void ftrace_trace_userstack(struct trace_array *tr, @@ -3374,7 +3344,7 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args) pause_graph_tracing(); trace_ctx = tracing_gen_ctx(); - preempt_disable_notrace(); + guard(preempt_notrace)(); tbuffer = get_trace_buf(); if (!tbuffer) { @@ -3406,7 +3376,6 @@ out_put: put_trace_buf(); out_nobuffer: - preempt_enable_notrace(); unpause_graph_tracing(); return len; @@ -3430,7 +3399,7 @@ int __trace_array_vprintk(struct trace_buffer *buffer, pause_graph_tracing(); trace_ctx = tracing_gen_ctx(); - preempt_disable_notrace(); + guard(preempt_notrace)(); tbuffer = get_trace_buf(); @@ -3458,7 +3427,6 @@ out: put_trace_buf(); out_nobuffer: - preempt_enable_notrace(); unpause_graph_tracing(); return len; @@ -4788,20 +4756,16 @@ int tracing_open_file_tr(struct inode *inode, struct file *filp) if (ret) return ret; - mutex_lock(&event_mutex); + guard(mutex)(&event_mutex); /* Fail if the file is marked for removal */ if (file->flags & EVENT_FILE_FL_FREED) { trace_array_put(file->tr); - ret = -ENODEV; + return -ENODEV; } else { event_file_get(file); } - mutex_unlock(&event_mutex); - if (ret) - return ret; - filp->private_data = inode->i_private; return 0; @@ -5945,9 +5909,9 @@ tracing_set_trace_read(struct file *filp, char __user *ubuf, char buf[MAX_TRACER_SIZE+2]; int r; - mutex_lock(&trace_types_lock); - r = sprintf(buf, "%s\n", tr->current_trace->name); - mutex_unlock(&trace_types_lock); + scoped_guard(mutex, &trace_types_lock) { + r = sprintf(buf, "%s\n", tr->current_trace->name); + } return simple_read_from_buffer(ubuf, cnt, ppos, buf, r); } @@ -6249,15 +6213,13 @@ int tracing_update_buffers(struct trace_array *tr) { int ret = 0; - mutex_lock(&trace_types_lock); + guard(mutex)(&trace_types_lock); update_last_data(tr); if (!tr->ring_buffer_expanded) ret = __tracing_resize_ring_buffer(tr, trace_buf_size, RING_BUFFER_ALL_CPUS); - mutex_unlock(&trace_types_lock); - return ret; } @@ -6554,7 +6516,7 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp) if (ret) return ret; - mutex_lock(&trace_types_lock); + guard(mutex)(&trace_types_lock); cpu = tracing_get_cpu(inode); ret = open_pipe_on_cpu(tr, cpu); if (ret) @@ -6598,7 +6560,6 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp) tr->trace_ref++; - mutex_unlock(&trace_types_lock); return ret; fail: @@ -6607,7 +6568,6 @@ fail_alloc_iter: close_pipe_on_cpu(tr, cpu); fail_pipe_on_cpu: __trace_array_put(tr); - mutex_unlock(&trace_types_lock); return ret; } @@ -6616,14 +6576,13 @@ static int tracing_release_pipe(struct inode *inode, struct file *file) struct trace_iterator *iter = file->private_data; struct trace_array *tr = inode->i_private; - mutex_lock(&trace_types_lock); + scoped_guard(mutex, &trace_types_lock) { + tr->trace_ref--; - tr->trace_ref--; - - if (iter->trace->pipe_close) - iter->trace->pipe_close(iter); - close_pipe_on_cpu(tr, iter->cpu_file); - mutex_unlock(&trace_types_lock); + if (iter->trace->pipe_close) + iter->trace->pipe_close(iter); + close_pipe_on_cpu(tr, iter->cpu_file); + } free_trace_iter_content(iter); kfree(iter); @@ -7426,7 +7385,7 @@ int tracing_set_clock(struct trace_array *tr, const char *clockstr) if (i == ARRAY_SIZE(trace_clocks)) return -EINVAL; - mutex_lock(&trace_types_lock); + guard(mutex)(&trace_types_lock); tr->clock_id = i; @@ -7450,8 +7409,6 @@ int tracing_set_clock(struct trace_array *tr, const char *clockstr) tscratch->clock_id = i; } - mutex_unlock(&trace_types_lock); - return 0; } @@ -7503,15 +7460,13 @@ static int tracing_time_stamp_mode_show(struct seq_file *m, void *v) { struct trace_array *tr = m->private; - mutex_lock(&trace_types_lock); + guard(mutex)(&trace_types_lock); if (ring_buffer_time_stamp_abs(tr->array_buffer.buffer)) seq_puts(m, "delta [absolute]\n"); else seq_puts(m, "[delta] absolute\n"); - mutex_unlock(&trace_types_lock); - return 0; } @@ -8099,14 +8054,14 @@ static void clear_tracing_err_log(struct trace_array *tr) { struct tracing_log_err *err, *next; - mutex_lock(&tracing_err_log_lock); + guard(mutex)(&tracing_err_log_lock); + list_for_each_entry_safe(err, next, &tr->err_log, list) { list_del(&err->list); free_tracing_log_err(err); } tr->n_err_log_entries = 0; - mutex_unlock(&tracing_err_log_lock); } static void *tracing_err_log_seq_start(struct seq_file *m, loff_t *pos) @@ -8377,7 +8332,7 @@ static int tracing_buffers_release(struct inode *inode, struct file *file) struct ftrace_buffer_info *info = file->private_data; struct trace_iterator *iter = &info->iter; - mutex_lock(&trace_types_lock); + guard(mutex)(&trace_types_lock); iter->tr->trace_ref--; @@ -8388,8 +8343,6 @@ static int tracing_buffers_release(struct inode *inode, struct file *file) info->spare_cpu, info->spare); kvfree(info); - mutex_unlock(&trace_types_lock); - return 0; } @@ -8597,14 +8550,13 @@ static long tracing_buffers_ioctl(struct file *file, unsigned int cmd, unsigned * An ioctl call with cmd 0 to the ring buffer file will wake up all * waiters */ - mutex_lock(&trace_types_lock); + guard(mutex)(&trace_types_lock); /* Make sure the waiters see the new wait_index */ (void)atomic_fetch_inc_release(&iter->wait_index); ring_buffer_wake_waiters(iter->array_buffer->buffer, iter->cpu_file); - mutex_unlock(&trace_types_lock); return 0; } @@ -9094,10 +9046,9 @@ trace_options_write(struct file *filp, const char __user *ubuf, size_t cnt, return -EINVAL; if (!!(topt->flags->val & topt->opt->bit) != val) { - mutex_lock(&trace_types_lock); + guard(mutex)(&trace_types_lock); ret = __set_tracer_option(topt->tr, topt->flags, topt->opt, !val); - mutex_unlock(&trace_types_lock); if (ret) return ret; } @@ -9406,7 +9357,7 @@ rb_simple_write(struct file *filp, const char __user *ubuf, return ret; if (buffer) { - mutex_lock(&trace_types_lock); + guard(mutex)(&trace_types_lock); if (!!val == tracer_tracing_is_on(tr)) { val = 0; /* do nothing */ } else if (val) { @@ -9420,7 +9371,6 @@ rb_simple_write(struct file *filp, const char __user *ubuf, /* Wake up any waiters */ ring_buffer_wake_waiters(buffer, RING_BUFFER_ALL_CPUS); } - mutex_unlock(&trace_types_lock); } (*ppos)++; @@ -9804,10 +9754,9 @@ static void __update_tracer_options(struct trace_array *tr) static void update_tracer_options(struct trace_array *tr) { - mutex_lock(&trace_types_lock); + guard(mutex)(&trace_types_lock); tracer_options_updated = true; __update_tracer_options(tr); - mutex_unlock(&trace_types_lock); } /* Must have trace_types_lock held */ @@ -9829,11 +9778,10 @@ struct trace_array *trace_array_find_get(const char *instance) { struct trace_array *tr; - mutex_lock(&trace_types_lock); + guard(mutex)(&trace_types_lock); tr = trace_array_find(instance); if (tr) tr->ref++; - mutex_unlock(&trace_types_lock); return tr; } From 12d5189615862a9eb06d4aa7c8a990bcde2ebb01 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Fri, 1 Aug 2025 16:37:26 -0400 Subject: [PATCH 4/6] tracing: Use __free(kfree) in trace.c to remove gotos There's a couple of locations that have goto out in trace.c for the only purpose of freeing a variable that was allocated. These can be replaced with __free(kfree). Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Link: https://lore.kernel.org/20250801203858.040892777@kernel.org Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace.c | 36 ++++++++++++------------------------ 1 file changed, 12 insertions(+), 24 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 4299e89ed04e..d0b1964648c1 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5042,7 +5042,7 @@ tracing_cpumask_read(struct file *filp, char __user *ubuf, size_t count, loff_t *ppos) { struct trace_array *tr = file_inode(filp)->i_private; - char *mask_str; + char *mask_str __free(kfree) = NULL; int len; len = snprintf(NULL, 0, "%*pb\n", @@ -5053,16 +5053,10 @@ tracing_cpumask_read(struct file *filp, char __user *ubuf, len = snprintf(mask_str, len, "%*pb\n", cpumask_pr_args(tr->tracing_cpumask)); - if (len >= count) { - count = -EINVAL; - goto out_err; - } - count = simple_read_from_buffer(ubuf, count, ppos, mask_str, len); + if (len >= count) + return -EINVAL; -out_err: - kfree(mask_str); - - return count; + return simple_read_from_buffer(ubuf, count, ppos, mask_str, len); } int tracing_set_cpumask(struct trace_array *tr, @@ -10739,7 +10733,8 @@ ssize_t trace_parse_run_command(struct file *file, const char __user *buffer, size_t count, loff_t *ppos, int (*createfn)(const char *)) { - char *kbuf, *buf, *tmp; + char *kbuf __free(kfree) = NULL; + char *buf, *tmp; int ret = 0; size_t done = 0; size_t size; @@ -10754,10 +10749,9 @@ ssize_t trace_parse_run_command(struct file *file, const char __user *buffer, if (size >= WRITE_BUFSIZE) size = WRITE_BUFSIZE - 1; - if (copy_from_user(kbuf, buffer + done, size)) { - ret = -EFAULT; - goto out; - } + if (copy_from_user(kbuf, buffer + done, size)) + return -EFAULT; + kbuf[size] = '\0'; buf = kbuf; do { @@ -10773,8 +10767,7 @@ ssize_t trace_parse_run_command(struct file *file, const char __user *buffer, /* This can accept WRITE_BUFSIZE - 2 ('\n' + '\0') */ pr_warn("Line length is too long: Should be less than %d\n", WRITE_BUFSIZE - 2); - ret = -EINVAL; - goto out; + return -EINVAL; } } done += size; @@ -10787,17 +10780,12 @@ ssize_t trace_parse_run_command(struct file *file, const char __user *buffer, ret = createfn(buf); if (ret) - goto out; + return ret; buf += size; } while (done < count); } - ret = done; - -out: - kfree(kbuf); - - return ret; + return done; } #ifdef CONFIG_TRACER_MAX_TRACE From db5f0c3e3e60939bb2ecc2dbdea4e6f32252620b Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Fri, 1 Aug 2025 16:37:27 -0400 Subject: [PATCH 5/6] ring-buffer: Convert ring_buffer_write() to use guard(preempt_notrace) The function ring_buffer_write() has a goto out to only do a preempt_enable_notrace(). This can be replaced by a guard. Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Link: https://lore.kernel.org/20250801203858.205479143@kernel.org Signed-off-by: Steven Rostedt (Google) --- kernel/trace/ring_buffer.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 00fc38d70e86..9d7bf17fbfba 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -4714,26 +4714,26 @@ int ring_buffer_write(struct trace_buffer *buffer, int ret = -EBUSY; int cpu; - preempt_disable_notrace(); + guard(preempt_notrace)(); if (atomic_read(&buffer->record_disabled)) - goto out; + return -EBUSY; cpu = raw_smp_processor_id(); if (!cpumask_test_cpu(cpu, buffer->cpumask)) - goto out; + return -EBUSY; cpu_buffer = buffer->buffers[cpu]; if (atomic_read(&cpu_buffer->record_disabled)) - goto out; + return -EBUSY; if (length > buffer->max_data_size) - goto out; + return -EBUSY; if (unlikely(trace_recursive_lock(cpu_buffer))) - goto out; + return -EBUSY; event = rb_reserve_next_event(buffer, cpu_buffer, length); if (!event) @@ -4751,10 +4751,6 @@ int ring_buffer_write(struct trace_buffer *buffer, out_unlock: trace_recursive_unlock(cpu_buffer); - - out: - preempt_enable_notrace(); - return ret; } EXPORT_SYMBOL_GPL(ring_buffer_write); From 3ca824369b71d4b441e1fdcdee8e66bcb05510a9 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Fri, 1 Aug 2025 16:56:01 -0400 Subject: [PATCH 6/6] tracing: Have unsigned int function args displayed as hexadecimal Most function arguments that are passed in as unsigned int or unsigned long are better displayed as hexadecimal than normal integer. For example, the functions: static void __create_object(unsigned long ptr, size_t size, int min_count, gfp_t gfp, unsigned int objflags); static bool stack_access_ok(struct unwind_state *state, unsigned long _addr, size_t len); void __local_bh_disable_ip(unsigned long ip, unsigned int cnt); Show up in the trace as: __create_object(ptr=-131387050520576, size=4096, min_count=1, gfp=3264, objflags=0) <-kmem_cache_alloc_noprof stack_access_ok(state=0xffffc9000233fc98, _addr=-60473102566256, len=8) <-unwind_next_frame __local_bh_disable_ip(ip=-2127311112, cnt=256) <-handle_softirqs Instead, by displaying unsigned as hexadecimal, they look more like this: __create_object(ptr=0xffff8881028d2080, size=0x280, min_count=1, gfp=0x82820, objflags=0x0) <-kmem_cache_alloc_node_noprof stack_access_ok(state=0xffffc90000003938, _addr=0xffffc90000003930, len=0x8) <-unwind_next_frame __local_bh_disable_ip(ip=0xffffffff8133cef8, cnt=0x100) <-handle_softirqs Which is much easier to understand as most unsigned longs are usually just pointers. Even the "unsigned int cnt" in __local_bh_disable_ip() looks better as hexadecimal as a lot of flags are passed as unsigned. Changes since v2: https://lore.kernel.org/20250801111453.01502861@gandalf.local.home - Use btf_int_encoding() instead of open coding it (Martin KaFai Lau) Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Douglas Raillard Cc: Martin KaFai Lau Link: https://lore.kernel.org/20250801165601.7770d65c@gandalf.local.home Acked-by: Yonghong Song Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace_output.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index 0b3db02030a7..97db0b0ccf3e 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -701,6 +701,7 @@ void print_function_args(struct trace_seq *s, unsigned long *args, struct btf *btf; s32 tid, nr = 0; int a, p, x; + u16 encode; trace_seq_printf(s, "("); @@ -744,7 +745,12 @@ void print_function_args(struct trace_seq *s, unsigned long *args, trace_seq_printf(s, "0x%lx", arg); break; case BTF_KIND_INT: - trace_seq_printf(s, "%ld", arg); + encode = btf_int_encoding(t); + /* Print unsigned ints as hex */ + if (encode & BTF_INT_SIGNED) + trace_seq_printf(s, "%ld", arg); + else + trace_seq_printf(s, "0x%lx", arg); break; case BTF_KIND_ENUM: trace_seq_printf(s, "%ld", arg);