Work around an assert failure in the dynamic linker's default thread

locking functions.  If an application loads a shared object with
dlopen() and the shared object has an init function which requires
lazy binding, then _rtld_bind is called when the thread is already
inside the dynamic linker.  This leads to a recursive acquisition
of the lock, which I was not expecting -- hence the assert failure.

This work-around makes the default locking functions handle recursive
locking.  It is NOT the correct fix -- that should be implemented
at the generic locking level rather than in the default locking
functions.  I will implement the correct fix in a future commit.

Since the dllockinit() interface will likely need to change, warn
about that in both the man page and the header file.

4 files changed, 32 insertions, 16 deletions

diff --git a/libexec/rtld-elf/alpha/lockdflt.c b/libexec/rtld-elf/alpha/lockdflt.c
index 6f278c3..c926950 100644
--- a/libexec/rtld-elf/alpha/lockdflt.c
+++ b/libexec/rtld-elf/alpha/lockdflt.c
@@ -51,8 +51,11 @@ void
 lockdflt_acquire(void *lock)
 {
     LockDflt *l = (LockDflt *)lock;
-    sigprocmask(SIG_BLOCK, &l->lock_mask, &l->old_mask);
-    assert(l->depth == 0);
+    sigset_t old_mask;
+
+    sigprocmask(SIG_BLOCK, &l->lock_mask, &old_mask);
+    if (l->depth == 0)
+	l->old_mask = old_mask;
     l->depth++;
 }
 
@@ -81,9 +84,10 @@ void
 lockdflt_release(void *lock)
 {
     LockDflt *l = (LockDflt *)lock;
-    assert(l->depth == 1);
     l->depth--;
-    sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
+    assert(l->depth >= 0);
+    if (l->depth == 0)
+	sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
 }
 
 void
diff --git a/libexec/rtld-elf/amd64/lockdflt.c b/libexec/rtld-elf/amd64/lockdflt.c
index 6f278c3..c926950 100644
--- a/libexec/rtld-elf/amd64/lockdflt.c
+++ b/libexec/rtld-elf/amd64/lockdflt.c
@@ -51,8 +51,11 @@ void
 lockdflt_acquire(void *lock)
 {
     LockDflt *l = (LockDflt *)lock;
-    sigprocmask(SIG_BLOCK, &l->lock_mask, &l->old_mask);
-    assert(l->depth == 0);
+    sigset_t old_mask;
+
+    sigprocmask(SIG_BLOCK, &l->lock_mask, &old_mask);
+    if (l->depth == 0)
+	l->old_mask = old_mask;
     l->depth++;
 }
 
@@ -81,9 +84,10 @@ void
 lockdflt_release(void *lock)
 {
     LockDflt *l = (LockDflt *)lock;
-    assert(l->depth == 1);
     l->depth--;
-    sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
+    assert(l->depth >= 0);
+    if (l->depth == 0)
+	sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
 }
 
 void
diff --git a/libexec/rtld-elf/i386/lockdflt.c b/libexec/rtld-elf/i386/lockdflt.c
index 6f278c3..c926950 100644
--- a/libexec/rtld-elf/i386/lockdflt.c
+++ b/libexec/rtld-elf/i386/lockdflt.c
@@ -51,8 +51,11 @@ void
 lockdflt_acquire(void *lock)
 {
     LockDflt *l = (LockDflt *)lock;
-    sigprocmask(SIG_BLOCK, &l->lock_mask, &l->old_mask);
-    assert(l->depth == 0);
+    sigset_t old_mask;
+
+    sigprocmask(SIG_BLOCK, &l->lock_mask, &old_mask);
+    if (l->depth == 0)
+	l->old_mask = old_mask;
     l->depth++;
 }
 
@@ -81,9 +84,10 @@ void
 lockdflt_release(void *lock)
 {
     LockDflt *l = (LockDflt *)lock;
-    assert(l->depth == 1);
     l->depth--;
-    sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
+    assert(l->depth >= 0);
+    if (l->depth == 0)
+	sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
 }
 
 void
diff --git a/libexec/rtld-elf/lockdflt.c b/libexec/rtld-elf/lockdflt.c
index 6f278c3..c926950 100644
--- a/libexec/rtld-elf/lockdflt.c
+++ b/libexec/rtld-elf/lockdflt.c
@@ -51,8 +51,11 @@ void
 lockdflt_acquire(void *lock)
 {
     LockDflt *l = (LockDflt *)lock;
-    sigprocmask(SIG_BLOCK, &l->lock_mask, &l->old_mask);
-    assert(l->depth == 0);
+    sigset_t old_mask;
+
+    sigprocmask(SIG_BLOCK, &l->lock_mask, &old_mask);
+    if (l->depth == 0)
+	l->old_mask = old_mask;
     l->depth++;
 }
 
@@ -81,9 +84,10 @@ void
 lockdflt_release(void *lock)
 {
     LockDflt *l = (LockDflt *)lock;
-    assert(l->depth == 1);
     l->depth--;
-    sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
+    assert(l->depth >= 0);
+    if (l->depth == 0)
+	sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
 }
 
 void