Re: [PATCH v8 3/3] binder: add transaction latency tracer

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Mon, Sep 07, 2020 at 08:00:55PM +0800, Frankie Chang wrote:
> From: "Frankie.Chang" <Frankie.Chang@mediatek.com>
> 
> Record start/end timestamp for binder transaction.
> When transaction is completed or transaction is free,
> it would be checked if transaction latency over threshold
> (default 2 sec), if yes, printing related information for tracing.
> 
> /* Implement details */
> - Add latency tracer module to monitor transaction
>   by attaching to new tracepoints introduced
>   when transactions are allocated and freed.
>   The trace_binder_txn_latency_free would not be enabled
>   by default. Monitoring which transaction is too slow to
>   cause some of exceptions is important. So we hook the
>   tracepoint to call the monitor function.
> 
> - Since some of modules would trigger timeout NE
>   if their binder transaction don't finish in time,
>   such as audio timeout (5 sec), even BT command
>   timeout (2 sec), etc.
>   Therefore, setting the timeout threshold as default
>   2 seconds could be helpful to debug.
>   But this timeout threshold is configurable, to let
>   all users determine the more suitable threshold.
> 
> - The reason why printing the related information to
>   kernel information log but not trace buffer is that
>   some abnormal transactions may be pending for a long
>   time ago, they could not be recorded due to buffer
>   limited.
> 
> Signed-off-by: Frankie.Chang <Frankie.Chang@mediatek.com>
> Acked-by: Todd Kjos <tkjos@google.com>
> ---
>  drivers/android/Kconfig                 |    8 +++
>  drivers/android/Makefile                |    1 +
>  drivers/android/binder.c                |    6 ++
>  drivers/android/binder_internal.h       |   13 ++++
>  drivers/android/binder_latency_tracer.c |  112 +++++++++++++++++++++++++++++++
>  drivers/android/binder_trace.h          |   26 ++++++-
>  6 files changed, 163 insertions(+), 3 deletions(-)
>  create mode 100644 drivers/android/binder_latency_tracer.c
> 
> diff --git a/drivers/android/Kconfig b/drivers/android/Kconfig
> index 53b22e2..8aadaf4 100644
> --- a/drivers/android/Kconfig
> +++ b/drivers/android/Kconfig
> @@ -54,6 +54,14 @@ config ANDROID_BINDER_IPC_SELFTEST
>  	  exhaustively with combinations of various buffer sizes and
>  	  alignments.
>  
> +config BINDER_TRANSACTION_LATENCY_TRACKING
> +	tristate "Android Binder transaction tracking"
> +	help
> +	  Used for track abnormal binder transaction which is over threshold,
> +	  when the transaction is done or be free, this transaction would be
> +	  checked whether it executed overtime.
> +	  If yes, printing out the detailed info.
> +
>  endif # if ANDROID
>  
>  endmenu
> diff --git a/drivers/android/Makefile b/drivers/android/Makefile
> index c9d3d0c9..c2ffdb6 100644
> --- a/drivers/android/Makefile
> +++ b/drivers/android/Makefile
> @@ -4,3 +4,4 @@ ccflags-y += -I$(src)			# needed for trace events
>  obj-$(CONFIG_ANDROID_BINDERFS)		+= binderfs.o
>  obj-$(CONFIG_ANDROID_BINDER_IPC)	+= binder.o binder_alloc.o
>  obj-$(CONFIG_ANDROID_BINDER_IPC_SELFTEST) += binder_alloc_selftest.o
> +obj-$(CONFIG_BINDER_TRANSACTION_LATENCY_TRACKING)	+= binder_latency_tracer.o
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 0cab900..65ad38c 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -2674,6 +2674,7 @@ static void binder_transaction(struct binder_proc *proc,
>  		return_error_line = __LINE__;
>  		goto err_alloc_t_failed;
>  	}
> +	trace_binder_txn_latency_alloc(t);
>  	INIT_LIST_HEAD(&t->fd_fixups);
>  	binder_stats_created(BINDER_STAT_TRANSACTION);
>  	spin_lock_init(&t->lock);
> @@ -5177,6 +5178,7 @@ static void print_binder_transaction_ilocked(struct seq_file *m,
>  		   to_proc ? to_proc->pid : 0,
>  		   t->to_thread ? t->to_thread->pid : 0,
>  		   t->code, t->flags, t->priority, t->need_reply);
> +	trace_binder_txn_latency_info(m, t);
>  	spin_unlock(&t->lock);
>  
>  	if (proc != to_proc) {
> @@ -5818,4 +5820,8 @@ static int __init binder_init(void)
>  #define CREATE_TRACE_POINTS
>  #include "binder_trace.h"
>  
> +EXPORT_TRACEPOINT_SYMBOL(binder_txn_latency_alloc);
> +EXPORT_TRACEPOINT_SYMBOL(binder_txn_latency_info);
> +EXPORT_TRACEPOINT_SYMBOL(binder_txn_latency_free);
> +
>  MODULE_LICENSE("GPL v2");
> diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h
> index 872232f..309d1b10 100644
> --- a/drivers/android/binder_internal.h
> +++ b/drivers/android/binder_internal.h
> @@ -15,6 +15,11 @@
>  #include <uapi/linux/android/binderfs.h>
>  #include "binder_alloc.h"
>  
> +#if IS_ENABLED(CONFIG_BINDER_TRANSACTION_LATENCY_TRACKING)
> +#include <uapi/linux/time_types.h>
> +#include <linux/rtc.h>
> +#endif
> +
>  struct binder_context {
>  	struct binder_node *binder_context_mgr_node;
>  	struct mutex context_mgr_node_lock;
> @@ -524,6 +529,14 @@ struct binder_transaction {
>  	 * during thread teardown
>  	 */
>  	spinlock_t lock;
> +	/**
> +	 * @timestamp and @tv are used to record the time
> +	 * that the binder transaction startup
> +	 */
> +#if IS_ENABLED(CONFIG_BINDER_TRANSACTION_LATENCY_TRACKING)
> +	struct timespec64 timestamp;
> +	struct __kernel_old_timeval tv;

As I stated in the 0/3 email, please use the correct in-kernel structure
for this.  That structure is _ONLY_ for old userspace api compatibility
issues.  Which is not the case here at all.

thanks,

greg k-h