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Date:: Mon May 18 00:15:41 2020 UTC
Message:: libthread: add pthreadperthread mode and use under ASAN ASAN can't deal with the coroutine stacks. In theory we can call into ASAN runtime to let it know about them, but ASAN still has problems with fork or exit happening from a non-system stack. Bypass all possible problems by just having a full OS thread for each libthread thread. The threads are still cooperatively scheduled within a proc (in thos mode, a group of OS threads). Setting the environment variable LIBTHREAD=pthreadperthread will enable the pthreadperthread mode, as will building with CC9FLAGS='-fsanitize=address' in $PLAN9/config. This solution is much more general than ASAN - for example if you are trying to find all the thread stacks in a reproducible crash you can use pthreadperthread mode with any debugger that knows only about OS threads.
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1 #include "u.h"
2 #include <errno.h>
3 #include <sys/time.h>
4 #include <sys/types.h>
5 #include <sys/wait.h>
6 #include <sched.h>
7 #include <signal.h>
8 #if !defined(__OpenBSD__)
9 #	if defined(__APPLE__)
10 #		define _XOPEN_SOURCE 	/* for Snow Leopard */
11 #	endif
12 #	include <ucontext.h>
13 #endif
14 #include <sys/utsname.h>
15 #include "libc.h"
16 #include "thread.h"
17 
18 #if defined(__APPLE__)
19 	/*
20 	 * OS X before 10.5 (Leopard) does not provide
21 	 * swapcontext nor makecontext, so we have to use our own.
22 	 * In theory, Leopard does provide them, but when we use
23 	 * them, they seg fault.  Maybe we're using them wrong.
24 	 * So just use our own versions, even on Leopard.
25 	 */
26 #	define mcontext libthread_mcontext
27 #	define mcontext_t libthread_mcontext_t
28 #	define ucontext libthread_ucontext
29 #	define ucontext_t libthread_ucontext_t
30 #	define swapcontext libthread_swapcontext
31 #	define makecontext libthread_makecontext
32 #	if defined(__i386__)
33 #		include "386-ucontext.h"
34 #	elif defined(__x86_64__)
35 #		include "x86_64-ucontext.h"
36 #	elif defined(__ppc__) || defined(__power__)
37 #		include "power-ucontext.h"
38 #	else
39 #		error "unknown architecture"
40 #	endif
41 #endif
42 
43 #if defined(__OpenBSD__)
44 #	define mcontext libthread_mcontext
45 #	define mcontext_t libthread_mcontext_t
46 #	define ucontext libthread_ucontext
47 #	define ucontext_t libthread_ucontext_t
48 #	if defined __i386__
49 #		include "386-ucontext.h"
50 #	elif defined __amd64__
51 #		include "x86_64-ucontext.h"
52 #	else
53 #		include "power-ucontext.h"
54 #	endif
55 extern pid_t rfork_thread(int, void*, int(*)(void*), void*);
56 #endif
57 
58 #if defined(__arm__)
59 int mygetmcontext(ulong*);
60 void mysetmcontext(const ulong*);
61 #define	setcontext(u)	mysetmcontext(&(u)->uc_mcontext.arm_r0)
62 #define	getcontext(u)	mygetmcontext(&(u)->uc_mcontext.arm_r0)
63 #endif
64 
65 
66 typedef struct Context Context;
67 typedef struct Execjob Execjob;
68 typedef struct Proc Proc;
69 typedef struct _Procrendez _Procrendez;
70 
71 typedef struct Jmp Jmp;
72 struct Jmp
73 {
74 	p9jmp_buf b;
75 };
76 
77 enum
78 {
79 	STACK = 8192
80 };
81 
82 struct Context
83 {
84 	ucontext_t	uc;
85 #ifdef __APPLE__
86 	/*
87 	 * On Snow Leopard, etc., the context routines exist,
88 	 * so we use them, but apparently they write past the
89 	 * end of the ucontext_t.  Sigh.  We put some extra
90 	 * scratch space here for them.
91 	 */
92 	uchar	buf[1024];
93 #endif
94 };
95 
96 struct Execjob
97 {
98 	int *fd;
99 	char *cmd;
100 	char **argv;
101 	char *dir;
102 	Channel *c;
103 };
104 
105 struct _Procrendez
106 {
107 	Lock		*l;
108 	int		asleep;
109 #ifdef PLAN9PORT_USING_PTHREADS
110 	pthread_cond_t	cond;
111 #else
112 	int		pid;
113 #endif
114 };
115 
116 struct _Thread
117 {
118 	_Thread	*next;
119 	_Thread	*prev;
120 	_Thread	*allnext;
121 	_Thread	*allprev;
122 	Context	context;
123 	void	(*startfn)(void*);
124 	void	*startarg;
125 	uint	id;
126 #ifdef PLAN9PORT_USING_PTHREADS
127 	pthread_t	osprocid;
128 #else
129 	int		osprocid;
130 #endif
131 	uchar	*stk;
132 	uint	stksize;
133 	int		exiting;
134 	Proc	*proc;
135 	char	name[256];
136 	char	state[256];
137 	void *udata;
138 	Alt	*alt;
139 	_Procrendez schedrend;
140 };
141 
142 extern	void	_procsleep(_Procrendez*);
143 extern	void	_procwakeup(_Procrendez*);
144 extern	void	_procwakeupandunlock(_Procrendez*);
145 
146 struct Proc
147 {
148 	Proc		*next;
149 	Proc		*prev;
150 	char		msg[128];
151 #ifdef PLAN9PORT_USING_PTHREADS
152 	pthread_t	osprocid;
153 #else
154 	int		osprocid;
155 #endif
156 	Lock		lock;
157 	int			nswitch;
158 	_Thread		*thread0;
159 	_Thread		*thread;
160 	_Thread		*pinthread;
161 	_Threadlist	runqueue;
162 	_Threadlist	idlequeue;
163 	_Threadlist	allthreads;
164 	uint		nthread;
165 	uint		sysproc;
166 	_Procrendez	runrend;
167 	Lock		schedlock;
168 	_Thread	*schedthread;
169 	Context	schedcontext;
170 	void		*udata;
171 	Jmp		sigjmp;
172 	int		mainproc;
173 };
174 
175 #define proc() _threadproc()
176 
177 extern Proc *_threadprocs;
178 extern Lock _threadprocslock;
179 extern Proc *_threadexecproc;
180 extern Channel *_threadexecchan;
181 extern QLock _threadexeclock;
182 extern Channel *_dowaitchan;
183 
184 extern void _procstart(Proc*, void (*fn)(Proc*));
185 extern _Thread *_threadcreate(Proc*, void(*fn)(void*), void*, uint);
186 extern void _procexit(void);
187 extern Proc *_threadproc(void);
188 extern void _threadsetproc(Proc*);
189 extern int _threadlock(Lock*, int, ulong);
190 extern void _threadunlock(Lock*, ulong);
191 extern void _pthreadinit(void);
192 extern int _threadspawn(int*, char*, char**, char*);
193 extern int _runthreadspawn(int*, char*, char**, char*);
194 extern void _threadsetupdaemonize(void);
195 extern void _threaddodaemonize(char*);
196 extern void _threadpexit(void);
197 extern void _threaddaemonize(void);
198 extern void *_threadstkalloc(int);
199 extern void _threadstkfree(void*, int);
200 extern void _threadpthreadmain(Proc*, _Thread*);
201 extern void _threadpthreadstart(Proc*, _Thread*);
202 
203 #define USPALIGN(ucp, align) \
204 	(void*)((((uintptr)(ucp)->uc_stack.ss_sp+(ucp)->uc_stack.ss_size)-(align))&~((align)-1))