tracing: Fix complicated dependency of CONFIG_TRACER_MAX_TRACE

Both CONFIG_OSNOISE_TRACER and CONFIG_HWLAT_TRACER partially enables the
CONFIG_TRACER_MAX_TRACE code, but that is complicated and has
introduced a bug; It declares tracing_max_lat_fops data structure outside
of #ifdefs, but since it is defined only when CONFIG_TRACER_MAX_TRACE=y
or CONFIG_HWLAT_TRACER=y, if only CONFIG_OSNOISE_TRACER=y, that
declaration comes to a definition(!).

To fix this issue, and do not repeat the similar problem, makes
CONFIG_OSNOISE_TRACER and CONFIG_HWLAT_TRACER enables the
CONFIG_TRACER_MAX_TRACE always. It has there benefits;
- Fix the tracing_max_lat_fops bug
- Simplify the #ifdefs
- CONFIG_TRACER_MAX_TRACE code is fully enabled, or not.

Link: https://lore.kernel.org/linux-trace-kernel/167033628155.4111793.12185405690820208159.stgit@devnote3
Fixes: 424b650f35c7 ("tracing: Fix missing osnoise tracer on max_latency")
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: stable@vger.kernel.org
Reported-by: David Howells <dhowells@redhat.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://lore.kernel.org/all/166992525941.1716618.13740663757583361463.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/all/202212052253.VuhZ2ulJ-lkp@intel.com/T/#u
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index e9e95c790b8ee769d12327e6328ebf9264bc4895..93d7249962833c53e44ea71e740a8913d1ac948d 100644 (file)
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -375,6 +375,7 @@ config SCHED_TRACER
 config HWLAT_TRACER
        bool "Tracer to detect hardware latencies (like SMIs)"
        select GENERIC_TRACER
+       select TRACER_MAX_TRACE
        help
         This tracer, when enabled will create one or more kernel threads,
         depending on what the cpumask file is set to, which each thread
@@ -410,6 +411,7 @@ config HWLAT_TRACER
 config OSNOISE_TRACER
        bool "OS Noise tracer"
        select GENERIC_TRACER
+       select TRACER_MAX_TRACE
        help
          In the context of high-performance computing (HPC), the Operating
          System Noise (osnoise) refers to the interference experienced by an

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 948f321b9df179440945c626eb5fd27506cb3bec..664619b3f1e17c59973041a8aa25e51be0c9d8c0 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1421,6 +1421,7 @@ int tracing_snapshot_cond_disable(struct trace_array *tr)
        return false;
 }
 EXPORT_SYMBOL_GPL(tracing_snapshot_cond_disable);
+#define free_snapshot(tr)      do { } while (0)
 #endif /* CONFIG_TRACER_SNAPSHOT */
 
 void tracer_tracing_off(struct trace_array *tr)
@@ -1692,6 +1693,8 @@ static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
 }
 
 unsigned long __read_mostly    tracing_thresh;
+
+#ifdef CONFIG_TRACER_MAX_TRACE
 static const struct file_operations tracing_max_lat_fops;
 
 #ifdef LATENCY_FS_NOTIFY
@@ -1748,18 +1751,14 @@ void latency_fsnotify(struct trace_array *tr)
        irq_work_queue(&tr->fsnotify_irqwork);
 }
 
-#elif defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER) \
-       || defined(CONFIG_OSNOISE_TRACER)
+#else /* !LATENCY_FS_NOTIFY */
 
 #define trace_create_maxlat_file(tr, d_tracer)                         \
        trace_create_file("tracing_max_latency", TRACE_MODE_WRITE,      \
                          d_tracer, &tr->max_latency, &tracing_max_lat_fops)
 
-#else
-#define trace_create_maxlat_file(tr, d_tracer)  do { } while (0)
 #endif
 
-#ifdef CONFIG_TRACER_MAX_TRACE
 /*
  * Copy the new maximum trace into the separate maximum-trace
  * structure. (this way the maximum trace is permanently saved,
@@ -1834,14 +1833,15 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu,
                ring_buffer_record_off(tr->max_buffer.buffer);
 
 #ifdef CONFIG_TRACER_SNAPSHOT
-       if (tr->cond_snapshot && !tr->cond_snapshot->update(tr, cond_data))
-               goto out_unlock;
+       if (tr->cond_snapshot && !tr->cond_snapshot->update(tr, cond_data)) {
+               arch_spin_unlock(&tr->max_lock);
+               return;
+       }
 #endif
        swap(tr->array_buffer.buffer, tr->max_buffer.buffer);
 
        __update_max_tr(tr, tsk, cpu);
 
- out_unlock:
        arch_spin_unlock(&tr->max_lock);
 }
 
@@ -1888,6 +1888,7 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
        __update_max_tr(tr, tsk, cpu);
        arch_spin_unlock(&tr->max_lock);
 }
+
 #endif /* CONFIG_TRACER_MAX_TRACE */
 
 static int wait_on_pipe(struct trace_iterator *iter, int full)
@@ -6577,7 +6578,7 @@ out:
        return ret;
 }
 
-#if defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER)
+#ifdef CONFIG_TRACER_MAX_TRACE
 
 static ssize_t
 tracing_max_lat_read(struct file *filp, char __user *ubuf,
@@ -7592,7 +7593,7 @@ static const struct file_operations tracing_thresh_fops = {
        .llseek         = generic_file_llseek,
 };
 
-#if defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER)
+#ifdef CONFIG_TRACER_MAX_TRACE
 static const struct file_operations tracing_max_lat_fops = {
        .open           = tracing_open_generic,
        .read           = tracing_max_lat_read,
@@ -9606,7 +9607,9 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
 
        create_trace_options_dir(tr);
 
+#ifdef CONFIG_TRACER_MAX_TRACE
        trace_create_maxlat_file(tr, d_tracer);
+#endif
 
        if (ftrace_create_function_files(tr, d_tracer))
                MEM_FAIL(1, "Could not allocate function filter files");

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 8f37ff032b4f868e397b3522df5a42edf7c8dd10..9dc920b01c17f15f4fd0c15c455eeaf5e64f9469 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -308,8 +308,7 @@ struct trace_array {
        struct array_buffer     max_buffer;
        bool                    allocated_snapshot;
 #endif
-#if defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER) \
-       || defined(CONFIG_OSNOISE_TRACER)
+#ifdef CONFIG_TRACER_MAX_TRACE
        unsigned long           max_latency;
 #ifdef CONFIG_FSNOTIFY
        struct dentry           *d_max_latency;
@@ -688,12 +687,11 @@ void update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu,
                   void *cond_data);
 void update_max_tr_single(struct trace_array *tr,
                          struct task_struct *tsk, int cpu);
-#endif /* CONFIG_TRACER_MAX_TRACE */
 
-#if (defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER) \
-       || defined(CONFIG_OSNOISE_TRACER)) && defined(CONFIG_FSNOTIFY)
+#ifdef CONFIG_FSNOTIFY
 #define LATENCY_FS_NOTIFY
 #endif
+#endif /* CONFIG_TRACER_MAX_TRACE */
 
 #ifdef LATENCY_FS_NOTIFY
 void latency_fsnotify(struct trace_array *tr);