From baef953da253314657be9adea8f371bfbf4ba09e Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@swtch.com>
Date: Sun, 17 May 2020 08:24:54 -0400
Subject: 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.
---
 src/libthread/threadimpl.h | 33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

(limited to 'src/libthread/threadimpl.h')

diff --git a/src/libthread/threadimpl.h b/src/libthread/threadimpl.h
index cceb1b8e..c7373843 100644
--- a/src/libthread/threadimpl.h
+++ b/src/libthread/threadimpl.h
@@ -102,6 +102,17 @@ struct Execjob
 	Channel *c;
 };
 
+struct _Procrendez
+{
+	Lock		*l;
+	int		asleep;
+#ifdef PLAN9PORT_USING_PTHREADS
+	pthread_cond_t	cond;
+#else
+	int		pid;
+#endif
+};
+
 struct _Thread
 {
 	_Thread	*next;
@@ -112,6 +123,11 @@ struct _Thread
 	void	(*startfn)(void*);
 	void	*startarg;
 	uint	id;
+#ifdef PLAN9PORT_USING_PTHREADS
+	pthread_t	osprocid;
+#else
+	int		osprocid;
+#endif
 	uchar	*stk;
 	uint	stksize;
 	int		exiting;
@@ -120,17 +136,7 @@ struct _Thread
 	char	state[256];
 	void *udata;
 	Alt	*alt;
-};
-
-struct _Procrendez
-{
-	Lock		*l;
-	int		asleep;
-#ifdef PLAN9PORT_USING_PTHREADS
-	pthread_cond_t	cond;
-#else
-	int		pid;
-#endif
+	_Procrendez schedrend;
 };
 
 extern	void	_procsleep(_Procrendez*);
@@ -149,6 +155,7 @@ struct Proc
 #endif
 	Lock		lock;
 	int			nswitch;
+	_Thread		*thread0;
 	_Thread		*thread;
 	_Thread		*pinthread;
 	_Threadlist	runqueue;
@@ -157,6 +164,8 @@ struct Proc
 	uint		nthread;
 	uint		sysproc;
 	_Procrendez	runrend;
+	Lock		schedlock;
+	_Thread	*schedthread;
 	Context	schedcontext;
 	void		*udata;
 	Jmp		sigjmp;
@@ -188,6 +197,8 @@ extern void _threadpexit(void);
 extern void _threaddaemonize(void);
 extern void *_threadstkalloc(int);
 extern void _threadstkfree(void*, int);
+extern void _threadpthreadmain(Proc*, _Thread*);
+extern void _threadpthreadstart(Proc*, _Thread*);
 
 #define USPALIGN(ucp, align) \
 	(void*)((((uintptr)(ucp)->uc_stack.ss_sp+(ucp)->uc_stack.ss_size)-(align))&~((align)-1))
-- 
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