Merge remote-tracking branch 'origin/stable/10' into devel

1 files changed, 46 insertions, 18 deletions

diff --git a/sys/kern/kern_thr.c b/sys/kern/kern_thr.c
index 98965b1..b01aecb 100644
--- a/sys/kern/kern_thr.c
+++ b/sys/kern/kern_thr.c
@@ -36,6 +36,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/priv.h>
 #include <sys/proc.h>
 #include <sys/posix4.h>
+#include <sys/ptrace.h>
 #include <sys/racct.h>
 #include <sys/resourcevar.h>
 #include <sys/rwlock.h>
@@ -252,6 +253,8 @@ thread_create(struct thread *td, struct rtprio *rtp,
 	thread_unlock(td);
 	if (P_SHOULDSTOP(p))
 		newtd->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
+	if (p->p_ptevents & PTRACE_LWP)
+		newtd->td_dbgflags |= TDB_BORN;
 	PROC_UNLOCK(p);
 
 	tidhash_add(newtd);
@@ -314,29 +317,54 @@ kern_thr_exit(struct thread *td)
 
 	p = td->td_proc;
 
-	rw_wlock(&tidhash_lock);
+	/*
+	 * If all of the threads in a process call this routine to
+	 * exit (e.g. all threads call pthread_exit()), exactly one
+	 * thread should return to the caller to terminate the process
+	 * instead of the thread.
+	 *
+	 * Checking p_numthreads alone is not sufficient since threads
+	 * might be committed to terminating while the PROC_LOCK is
+	 * dropped in either ptracestop() or while removing this thread
+	 * from the tidhash.  Instead, the p_pendingexits field holds
+	 * the count of threads in either of those states and a thread
+	 * is considered the "last" thread if all of the other threads
+	 * in a process are already terminating.
+	 */
 	PROC_LOCK(p);
-
-	if (p->p_numthreads != 1) {
-		racct_sub(p, RACCT_NTHR, 1);
-		LIST_REMOVE(td, td_hash);
-		rw_wunlock(&tidhash_lock);
-		tdsigcleanup(td);
-		umtx_thread_exit(td);
-		PROC_SLOCK(p);
-		thread_stopped(p);
-		thread_exit();
-		/* NOTREACHED */
+	if (p->p_numthreads == p->p_pendingexits + 1) {
+		/*
+		 * Ignore attempts to shut down last thread in the
+		 * proc.  This will actually call _exit(2) in the
+		 * usermode trampoline when it returns.
+		 */
+		PROC_UNLOCK(p);
+		return (0);
 	}
 
+	p->p_pendingexits++;
+	td->td_dbgflags |= TDB_EXIT;
+	if (p->p_ptevents & PTRACE_LWP)
+		ptracestop(td, SIGTRAP);
+	PROC_UNLOCK(p);
+	tidhash_remove(td);
+	PROC_LOCK(p);
+	p->p_pendingexits--;
+
 	/*
-	 * Ignore attempts to shut down last thread in the proc.  This
-	 * will actually call _exit(2) in the usermode trampoline when
-	 * it returns.
+	 * The check above should prevent all other threads from this
+	 * process from exiting while the PROC_LOCK is dropped, so
+	 * there must be at least one other thread other than the
+	 * current thread.
 	 */
-	PROC_UNLOCK(p);
-	rw_wunlock(&tidhash_lock);
-	return (0);
+	KASSERT(p->p_numthreads > 1, ("too few threads"));
+	racct_sub(p, RACCT_NTHR, 1);
+	tdsigcleanup(td);
+	umtx_thread_exit(td);
+	PROC_SLOCK(p);
+	thread_stopped(p);
+	thread_exit();
+	/* NOTREACHED */
 }
 
 int