From b4a7c266b5d2c4c44090d51bb325d16a6318fbcb Mon Sep 17 00:00:00 2001
From: mittorn <mittorn@disroot.org>
Date: Sun, 24 Dec 2023 07:46:09 +0300
Subject: [PATCH] platform/linux: implement debug timers and cl_maxframetime to
 catch very long frames on debugger

---
 engine/client/cl_main.c           |  4 +++
 engine/client/cl_view.c           |  1 +
 engine/platform/linux/sys_linux.c | 45 +++++++++++++++++++++++++++++++
 engine/platform/platform.h        |  8 ++++++
 4 files changed, 58 insertions(+)

diff --git a/engine/client/cl_main.c b/engine/client/cl_main.c
index 182a8354..8950f9bf 100644
--- a/engine/client/cl_main.c
+++ b/engine/client/cl_main.c
@@ -87,6 +87,7 @@ static CVAR_DEFINE_AUTO( model, "", FCVAR_USERINFO|FCVAR_ARCHIVE|FCVAR_FILTERABL
 static CVAR_DEFINE_AUTO( topcolor, "0", FCVAR_USERINFO|FCVAR_ARCHIVE|FCVAR_FILTERABLE, "player top color" );
 static CVAR_DEFINE_AUTO( bottomcolor, "0", FCVAR_USERINFO|FCVAR_ARCHIVE|FCVAR_FILTERABLE, "player bottom color" );
 CVAR_DEFINE_AUTO( rate, "3500", FCVAR_USERINFO|FCVAR_ARCHIVE|FCVAR_FILTERABLE, "player network rate" );
+static CVAR_DEFINE_AUTO( cl_maxframetime, "0", 0, "set deadline timer for client rendering to catch freezes" );
 
 client_t		cl;
 client_static_t	cls;
@@ -2917,6 +2918,7 @@ void CL_InitLocal( void )
 	Cvar_RegisterVariable( &cl_showevents );
 	Cvar_Get( "lastdemo", "", FCVAR_ARCHIVE, "last played demo" );
 	Cvar_RegisterVariable( &ui_renderworld );
+	Cvar_RegisterVariable( &cl_maxframetime );
 
 	// these two added to shut up CS 1.5 about 'unknown' commands
 	Cvar_Get( "lightgamma", "1", FCVAR_ARCHIVE, "ambient lighting level (legacy, unused)" );
@@ -3057,6 +3059,8 @@ void Host_ClientFrame( void )
 {
 	// if client is not active, do nothing
 	if( !cls.initialized ) return;
+	if( cls.key_dest == key_game && cls.state == ca_active && !Con_Visible() )
+		Platform_SetTimer( cl_maxframetime.value );
 
 	// if running the server remotely, send intentions now after
 	// the incoming messages have been read
diff --git a/engine/client/cl_view.c b/engine/client/cl_view.c
index 477b5be4..f3fa4ca3 100644
--- a/engine/client/cl_view.c
+++ b/engine/client/cl_view.c
@@ -549,5 +549,6 @@ void V_PostRender( void )
 
 	SCR_MakeScreenShot();
 	ref.dllFuncs.R_AllowFog( true );
+	Platform_SetTimer( 0.0f );
 	ref.dllFuncs.R_EndFrame();
 }
diff --git a/engine/platform/linux/sys_linux.c b/engine/platform/linux/sys_linux.c
index 0734dbc3..860cd7d4 100644
--- a/engine/platform/linux/sys_linux.c
+++ b/engine/platform/linux/sys_linux.c
@@ -17,6 +17,10 @@ GNU General Public License for more details.
 #include <stdlib.h>
 #include <fcntl.h>
 #include <dlfcn.h>
+#include <signal.h>
+#include <ucontext.h>
+#include <time.h>
+#include <unistd.h>
 #include "platform/platform.h"
 
 static void *g_hsystemd;
@@ -103,3 +107,44 @@ void Linux_Shutdown( void )
 		g_hsystemd = NULL;
 	}
 }
+
+static void Linux_TimerHandler( int sig, siginfo_t *si, void *uc )
+{
+	timer_t  *tidp = si->si_value.sival_ptr;
+	int overrun = timer_getoverrun( *tidp );
+	Con_Printf( "Frame too long (overrun %d)!\n", overrun );
+}
+
+#define DEBUG_TIMER_SIGNAL SIGRTMIN
+
+void Linux_SetTimer( float tm )
+{
+	static timer_t timerid;
+
+	if( !timerid && tm )
+	{
+		struct sigevent    sev = { 0 };
+		struct sigaction   sa = { 0 };
+
+		sa.sa_flags = SA_SIGINFO;
+		sa.sa_sigaction = Linux_TimerHandler;
+		sigaction( DEBUG_TIMER_SIGNAL, &sa, NULL );
+		// this path availiable in POSIX, but may signal wrong thread...
+		// sev.sigev_notify = SIGEV_SIGNAL;
+		sev.sigev_notify = SIGEV_THREAD_ID;
+		sev._sigev_un._tid  = gettid();
+		sev.sigev_signo = DEBUG_TIMER_SIGNAL;
+		sev.sigev_value.sival_ptr = &timerid;
+		timer_create( CLOCK_REALTIME, &sev, &timerid );
+	}
+
+	if( timerid )
+	{
+		struct itimerspec  its = {0};
+		its.it_value.tv_sec = tm;
+		its.it_value.tv_nsec = 1000000000ULL * fmod( tm, 1.0f );
+		its.it_interval.tv_sec = 0;
+		its.it_interval.tv_nsec = 0;
+		timer_settime( timerid, 0, &its, NULL );
+	}
+}
diff --git a/engine/platform/platform.h b/engine/platform/platform.h
index a4dffb99..5482c784 100644
--- a/engine/platform/platform.h
+++ b/engine/platform/platform.h
@@ -91,6 +91,7 @@ void DOS_Shutdown( void );
 #if XASH_LINUX
 void Linux_Init( void );
 void Linux_Shutdown( void );
+void Linux_SetTimer( float time );
 #endif
 
 static inline void Platform_Init( void )
@@ -181,6 +182,13 @@ void Platform_SetClipboardText( const char *buffer );
 #define SDL_VERSION_ATLEAST( x, y, z ) 0
 #endif
 
+static void Platform_SetTimer( float time )
+{
+#if XASH_LINUX
+	Linux_SetTimer( time );
+#endif
+}
+
 /*
 ==============================================================================