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authorUlrich Drepper <drepper@redhat.com>1998-10-29 15:17:25 +0000
committerUlrich Drepper <drepper@redhat.com>1998-10-29 15:17:25 +0000
commitc5e340c71ba6f4563ca5fa245baa82b6363ddb2e (patch)
tree3ff655dfee624df411e1f3ebc062181fc0f3f338
parent05e951cd1ae7917ce25ec96cc17ebcbf401e345c (diff)
downloadglibc-c5e340c71ba6f4563ca5fa245baa82b6363ddb2e.tar.gz
glibc-c5e340c71ba6f4563ca5fa245baa82b6363ddb2e.tar.xz
glibc-c5e340c71ba6f4563ca5fa245baa82b6363ddb2e.zip
Update.
1998-10-29  Ulrich Drepper  <drepper@cygnus.com>

	* sysdeps/unix/sysv/linux/ttyname_r.c (ttyname_r): Try reading
	/prof/self/fd/FD first.
	* sysdeps/unix/sysv/linux/ttyname.c (ttyname): Likewise.

	* stdio-common/_itoa.h (_fitoa_word): New inline function.  Write
	formatted number starting at given position and return pointer to
	following byte.
	(_fitoa): Likewise, for long long.
-rw-r--r--ChangeLog11
-rw-r--r--linuxthreads/cancel.c2
-rw-r--r--linuxthreads/condvar.c14
-rw-r--r--linuxthreads/join.c8
-rw-r--r--linuxthreads/manager.c6
-rw-r--r--linuxthreads/mutex.c6
-rw-r--r--linuxthreads/pthread.c4
-rw-r--r--linuxthreads/rwlock.c17
-rw-r--r--linuxthreads/semaphore.c11
-rw-r--r--linuxthreads/signals.c2
-rw-r--r--linuxthreads/spinlock.c20
-rw-r--r--stdio-common/_itoa.h22
-rw-r--r--sysdeps/unix/sysv/linux/ttyname.c22
-rw-r--r--sysdeps/unix/sysv/linux/ttyname_r.c15
14 files changed, 109 insertions, 51 deletions
diff --git a/ChangeLog b/ChangeLog
index d32fbc39e5..3ad6c72dd4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+1998-10-29  Ulrich Drepper  <drepper@cygnus.com>
+
+	* sysdeps/unix/sysv/linux/ttyname_r.c (ttyname_r): Try reading
+	/prof/self/fd/FD first.
+	* sysdeps/unix/sysv/linux/ttyname.c (ttyname): Likewise.
+
+	* stdio-common/_itoa.h (_fitoa_word): New inline function.  Write
+	formatted number starting at given position and return pointer to
+	following byte.
+	(_fitoa): Likewise, for long long.
+
 1998-10-29  Roland McGrath  <roland@baalperazim.frob.com>
 
 	* sysdeps/unix/sysv/linux/bits/sem.h,
diff --git a/linuxthreads/cancel.c b/linuxthreads/cancel.c
index 3ff595418b..c45cac97a3 100644
--- a/linuxthreads/cancel.c
+++ b/linuxthreads/cancel.c
@@ -53,7 +53,7 @@ int pthread_cancel(pthread_t thread)
   pthread_handle handle = thread_handle(thread);
   int pid;
 
-  __pthread_lock(&handle->h_lock);
+  __pthread_lock(&handle->h_lock, NULL);
   if (invalid_handle(handle, thread)) {
     __pthread_unlock(&handle->h_lock);
     return ESRCH;
diff --git a/linuxthreads/condvar.c b/linuxthreads/condvar.c
index b880a38a73..cd22a241af 100644
--- a/linuxthreads/condvar.c
+++ b/linuxthreads/condvar.c
@@ -43,7 +43,7 @@ int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 {
   volatile pthread_descr self = thread_self();
 
-  __pthread_lock(&cond->__c_lock);
+  __pthread_lock(&cond->__c_lock, self);
   enqueue(&cond->__c_waiting, self);
   __pthread_unlock(&cond->__c_lock);
   pthread_mutex_unlock(mutex);
@@ -53,7 +53,7 @@ int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
   if (THREAD_GETMEM(self, p_canceled)
       && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
     /* Remove ourselves from the waiting queue if we're still on it */
-    __pthread_lock(&cond->__c_lock);
+    __pthread_lock(&cond->__c_lock, self);
     remove_from_queue(&cond->__c_waiting, self);
     __pthread_unlock(&cond->__c_lock);
     pthread_exit(PTHREAD_CANCELED);
@@ -72,7 +72,7 @@ pthread_cond_timedwait_relative(pthread_cond_t *cond,
   sigjmp_buf jmpbuf;
 
   /* Wait on the condition */
-  __pthread_lock(&cond->__c_lock);
+  __pthread_lock(&cond->__c_lock, self);
   enqueue(&cond->__c_waiting, self);
   __pthread_unlock(&cond->__c_lock);
   pthread_mutex_unlock(mutex);
@@ -107,7 +107,7 @@ pthread_cond_timedwait_relative(pthread_cond_t *cond,
   /* This is a cancellation point */
   if (THREAD_GETMEM(self, p_canceled)
       && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
-    __pthread_lock(&cond->__c_lock);
+    __pthread_lock(&cond->__c_lock, self);
     remove_from_queue(&cond->__c_waiting, self);
     __pthread_unlock(&cond->__c_lock);
     pthread_mutex_lock(mutex);
@@ -115,7 +115,7 @@ pthread_cond_timedwait_relative(pthread_cond_t *cond,
   }
   /* If not signaled: also remove ourselves and return an error code */
   if (THREAD_GETMEM(self, p_signal) == 0) {
-    __pthread_lock(&cond->__c_lock);
+    __pthread_lock(&cond->__c_lock, self);
     remove_from_queue(&cond->__c_waiting, self);
     __pthread_unlock(&cond->__c_lock);
     pthread_mutex_lock(mutex);
@@ -147,7 +147,7 @@ int pthread_cond_signal(pthread_cond_t *cond)
 {
   pthread_descr th;
 
-  __pthread_lock(&cond->__c_lock);
+  __pthread_lock(&cond->__c_lock, NULL);
   th = dequeue(&cond->__c_waiting);
   __pthread_unlock(&cond->__c_lock);
   if (th != NULL) restart(th);
@@ -158,7 +158,7 @@ int pthread_cond_broadcast(pthread_cond_t *cond)
 {
   pthread_descr tosignal, th;
 
-  __pthread_lock(&cond->__c_lock);
+  __pthread_lock(&cond->__c_lock, NULL);
   /* Copy the current state of the waiting queue and empty it */
   tosignal = cond->__c_waiting;
   cond->__c_waiting = NULL;
diff --git a/linuxthreads/join.c b/linuxthreads/join.c
index 482f0d1dcc..42eb033746 100644
--- a/linuxthreads/join.c
+++ b/linuxthreads/join.c
@@ -35,7 +35,7 @@ void pthread_exit(void * retval)
   __pthread_perform_cleanup();
   __pthread_destroy_specifics();
   /* Store return value */
-  __pthread_lock(THREAD_GETMEM(self, p_lock));
+  __pthread_lock(THREAD_GETMEM(self, p_lock), self);
   THREAD_SETMEM(self, p_retval, retval);
   /* Say that we've terminated */
   THREAD_SETMEM(self, p_terminated, 1);
@@ -65,7 +65,7 @@ int pthread_join(pthread_t thread_id, void ** thread_return)
   pthread_handle handle = thread_handle(thread_id);
   pthread_descr th;
 
-  __pthread_lock(&handle->h_lock);
+  __pthread_lock(&handle->h_lock, self);
   if (invalid_handle(handle, thread_id)) {
     __pthread_unlock(&handle->h_lock);
     return ESRCH;
@@ -91,7 +91,7 @@ int pthread_join(pthread_t thread_id, void ** thread_return)
       th->p_joining = NULL;
       pthread_exit(PTHREAD_CANCELED);
     }
-    __pthread_lock(&handle->h_lock);
+    __pthread_lock(&handle->h_lock, self);
   }
   /* Get return value */
   if (thread_return != NULL) *thread_return = th->p_retval;
@@ -114,7 +114,7 @@ int pthread_detach(pthread_t thread_id)
   pthread_handle handle = thread_handle(thread_id);
   pthread_descr th;
 
-  __pthread_lock(&handle->h_lock);
+  __pthread_lock(&handle->h_lock, NULL);
   if (invalid_handle(handle, thread_id)) {
     __pthread_unlock(&handle->h_lock);
     return ESRCH;
diff --git a/linuxthreads/manager.c b/linuxthreads/manager.c
index b6107da1fb..eafff3f4a8 100644
--- a/linuxthreads/manager.c
+++ b/linuxthreads/manager.c
@@ -417,7 +417,7 @@ static void pthread_free(pthread_descr th)
   ASSERT(th->p_exited);
   /* Make the handle invalid */
   handle =  thread_handle(th->p_tid);
-  __pthread_lock(&handle->h_lock);
+  __pthread_lock(&handle->h_lock, NULL);
   handle->h_descr = NULL;
   handle->h_bottom = (char *)(-1L);
   __pthread_unlock(&handle->h_lock);
@@ -452,7 +452,7 @@ static void pthread_exited(pid_t pid)
       th->p_nextlive->p_prevlive = th->p_prevlive;
       th->p_prevlive->p_nextlive = th->p_nextlive;
       /* Mark thread as exited, and if detached, free its resources */
-      __pthread_lock(th->p_lock);
+      __pthread_lock(th->p_lock, NULL);
       th->p_exited = 1;
       detached = th->p_detached;
       __pthread_unlock(th->p_lock);
@@ -494,7 +494,7 @@ static void pthread_handle_free(pthread_t th_id)
   pthread_handle handle = thread_handle(th_id);
   pthread_descr th;
 
-  __pthread_lock(&handle->h_lock);
+  __pthread_lock(&handle->h_lock, NULL);
   if (invalid_handle(handle, th_id)) {
     /* pthread_reap_children has deallocated the thread already,
        nothing needs to be done */
diff --git a/linuxthreads/mutex.c b/linuxthreads/mutex.c
index d3ef78cfbe..7e5271b5ea 100644
--- a/linuxthreads/mutex.c
+++ b/linuxthreads/mutex.c
@@ -81,7 +81,7 @@ int __pthread_mutex_lock(pthread_mutex_t * mutex)
 
   switch(mutex->__m_kind) {
   case PTHREAD_MUTEX_FAST_NP:
-    __pthread_lock(&mutex->__m_lock);
+    __pthread_lock(&mutex->__m_lock, NULL);
     return 0;
   case PTHREAD_MUTEX_RECURSIVE_NP:
     self = thread_self();
@@ -89,14 +89,14 @@ int __pthread_mutex_lock(pthread_mutex_t * mutex)
       mutex->__m_count++;
       return 0;
     }
-    __pthread_lock(&mutex->__m_lock);
+    __pthread_lock(&mutex->__m_lock, self);
     mutex->__m_owner = self;
     mutex->__m_count = 0;
     return 0;
   case PTHREAD_MUTEX_ERRORCHECK_NP:
     self = thread_self();
     if (mutex->__m_owner == self) return EDEADLK;
-    __pthread_lock(&mutex->__m_lock);
+    __pthread_lock(&mutex->__m_lock, self);
     mutex->__m_owner = self;
     return 0;
   default:
diff --git a/linuxthreads/pthread.c b/linuxthreads/pthread.c
index d0c66d0329..bd4ea5a8c2 100644
--- a/linuxthreads/pthread.c
+++ b/linuxthreads/pthread.c
@@ -394,7 +394,7 @@ int pthread_setschedparam(pthread_t thread, int policy,
   pthread_handle handle = thread_handle(thread);
   pthread_descr th;
 
-  __pthread_lock(&handle->h_lock);
+  __pthread_lock(&handle->h_lock, NULL);
   if (invalid_handle(handle, thread)) {
     __pthread_unlock(&handle->h_lock);
     return ESRCH;
@@ -417,7 +417,7 @@ int pthread_getschedparam(pthread_t thread, int *policy,
   pthread_handle handle = thread_handle(thread);
   int pid, pol;
 
-  __pthread_lock(&handle->h_lock);
+  __pthread_lock(&handle->h_lock, NULL);
   if (invalid_handle(handle, thread)) {
     __pthread_unlock(&handle->h_lock);
     return ESRCH;
diff --git a/linuxthreads/rwlock.c b/linuxthreads/rwlock.c
index bff4e38fa8..1fb18a3f9e 100644
--- a/linuxthreads/rwlock.c
+++ b/linuxthreads/rwlock.c
@@ -57,7 +57,7 @@ pthread_rwlock_destroy (pthread_rwlock_t *rwlock)
   int readers;
   _pthread_descr writer;
 
-  __pthread_lock (&rwlock->__rw_lock);
+  __pthread_lock (&rwlock->__rw_lock, NULL);
   readers = rwlock->__rw_readers;
   writer = rwlock->__rw_writer;
   __pthread_unlock (&rwlock->__rw_lock);
@@ -72,11 +72,11 @@ pthread_rwlock_destroy (pthread_rwlock_t *rwlock)
 int
 pthread_rwlock_rdlock (pthread_rwlock_t *rwlock)
 {
-  pthread_descr self;
+  pthread_descr self = NULL;
 
   while (1)
     {
-      __pthread_lock (&rwlock->__rw_lock);
+      __pthread_lock (&rwlock->__rw_lock, self);
       if (rwlock->__rw_writer == NULL
 	  || (rwlock->__rw_kind == PTHREAD_RWLOCK_PREFER_READER_NP
 	      && rwlock->__rw_readers != 0))
@@ -84,7 +84,8 @@ pthread_rwlock_rdlock (pthread_rwlock_t *rwlock)
 	break;
 
       /* Suspend ourselves, then try again */
-      self = thread_self ();
+      if (self == NULL)
+	self = thread_self ();
       enqueue (&rwlock->__rw_read_waiting, self);
       __pthread_unlock (&rwlock->__rw_lock);
       suspend (self); /* This is not a cancellation point */
@@ -102,7 +103,7 @@ pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock)
 {
   int result = EBUSY;
 
-  __pthread_lock (&rwlock->__rw_lock);
+  __pthread_lock (&rwlock->__rw_lock, NULL);
   if (rwlock->__rw_writer == NULL
       || (rwlock->__rw_kind == PTHREAD_RWLOCK_PREFER_READER_NP
 	  && rwlock->__rw_readers != 0))
@@ -123,7 +124,7 @@ pthread_rwlock_wrlock (pthread_rwlock_t *rwlock)
 
   while(1)
     {
-      __pthread_lock (&rwlock->__rw_lock);
+      __pthread_lock (&rwlock->__rw_lock, self);
       if (rwlock->__rw_readers == 0 && rwlock->__rw_writer == NULL)
 	{
 	  rwlock->__rw_writer = self;
@@ -144,7 +145,7 @@ pthread_rwlock_trywrlock (pthread_rwlock_t *rwlock)
 {
   int result = EBUSY;
 
-  __pthread_lock (&rwlock->__rw_lock);
+  __pthread_lock (&rwlock->__rw_lock, NULL);
   if (rwlock->__rw_readers == 0 && rwlock->__rw_writer == NULL)
     {
       rwlock->__rw_writer = thread_self ();
@@ -162,7 +163,7 @@ pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
   pthread_descr torestart;
   pthread_descr th;
 
-  __pthread_lock (&rwlock->__rw_lock);
+  __pthread_lock (&rwlock->__rw_lock, NULL);
   if (rwlock->__rw_writer != NULL)
     {
       /* Unlocking a write lock.  */
diff --git a/linuxthreads/semaphore.c b/linuxthreads/semaphore.c
index af5f115a16..cb23a71a78 100644
--- a/linuxthreads/semaphore.c
+++ b/linuxthreads/semaphore.c
@@ -40,15 +40,14 @@ int sem_init(sem_t *sem, int pshared, unsigned int value)
 
 int sem_wait(sem_t * sem)
 {
-  volatile pthread_descr self;
+  volatile pthread_descr self = thread_self();
 
-  __pthread_lock((struct _pthread_fastlock *) &sem->sem_lock);
+  __pthread_lock((struct _pthread_fastlock *) &sem->sem_lock, self);
   if (sem->sem_value > 0) {
     sem->sem_value--;
     __pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
     return 0;
   }
-  self = thread_self();
   enqueue(&sem->sem_waiting, self);
   /* Wait for sem_post or cancellation */
   __pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
@@ -57,7 +56,7 @@ int sem_wait(sem_t * sem)
   if (THREAD_GETMEM(self, p_canceled)
       && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
     /* Remove ourselves from the waiting list if we're still on it */
-    __pthread_lock((struct _pthread_fastlock *) &sem->sem_lock);
+    __pthread_lock((struct _pthread_fastlock *) &sem->sem_lock, self);
     remove_from_queue(&sem->sem_waiting, self);
     __pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
     pthread_exit(PTHREAD_CANCELED);
@@ -70,7 +69,7 @@ int sem_trywait(sem_t * sem)
 {
   int retval;
 
-  __pthread_lock((struct _pthread_fastlock *) &sem->sem_lock);
+  __pthread_lock((struct _pthread_fastlock *) &sem->sem_lock, NULL);
   if (sem->sem_value == 0) {
     errno = EAGAIN;
     retval = -1;
@@ -88,7 +87,7 @@ int sem_post(sem_t * sem)
   struct pthread_request request;
 
   if (THREAD_GETMEM(self, p_in_sighandler) == NULL) {
-    __pthread_lock((struct _pthread_fastlock *) &sem->sem_lock);
+    __pthread_lock((struct _pthread_fastlock *) &sem->sem_lock, self);
     if (sem->sem_waiting == NULL) {
       if (sem->sem_value >= SEM_VALUE_MAX) {
         /* Overflow */
diff --git a/linuxthreads/signals.c b/linuxthreads/signals.c
index 5444ef73f3..e833778d53 100644
--- a/linuxthreads/signals.c
+++ b/linuxthreads/signals.c
@@ -53,7 +53,7 @@ int pthread_kill(pthread_t thread, int signo)
   pthread_handle handle = thread_handle(thread);
   int pid;
 
-  __pthread_lock(&handle->h_lock);
+  __pthread_lock(&handle->h_lock, NULL);
   if (invalid_handle(handle, thread)) {
     __pthread_unlock(&handle->h_lock);
     return ESRCH;
diff --git a/linuxthreads/spinlock.c b/linuxthreads/spinlock.c
index 172cb7afe4..00a8691e5b 100644
--- a/linuxthreads/spinlock.c
+++ b/linuxthreads/spinlock.c
@@ -36,17 +36,18 @@
    This is safe because there are no concurrent __pthread_unlock
    operations -- only the thread that locked the mutex can unlock it. */
 
-void __pthread_lock(struct _pthread_fastlock * lock)
+void internal_function __pthread_lock(struct _pthread_fastlock * lock,
+				      pthread_descr self)
 {
   long oldstatus, newstatus;
-  pthread_descr self = NULL;
 
   do {
     oldstatus = lock->__status;
     if (oldstatus == 0) {
       newstatus = 1;
     } else {
-      self = thread_self();
+      if (self == NULL)
+	self = thread_self();
       newstatus = (long) self;
     }
     if (self != NULL)
@@ -56,18 +57,7 @@ void __pthread_lock(struct _pthread_fastlock * lock)
   if (oldstatus != 0) suspend(self);
 }
 
-int __pthread_trylock(struct _pthread_fastlock * lock)
-{
-  long oldstatus;
-
-  do {
-    oldstatus = lock->__status;
-    if (oldstatus != 0) return EBUSY;
-  } while(! compare_and_swap(&lock->__status, 0, 1, &lock->__spinlock));
-  return 0;
-}
-
-void __pthread_unlock(struct _pthread_fastlock * lock)
+void internal_function __pthread_unlock(struct _pthread_fastlock * lock)
 {
   long oldstatus;
   pthread_descr thr, * ptr, * maxptr;
diff --git a/stdio-common/_itoa.h b/stdio-common/_itoa.h
index 2794912c91..976636907d 100644
--- a/stdio-common/_itoa.h
+++ b/stdio-common/_itoa.h
@@ -1,5 +1,5 @@
 /* Internal function for converting integers to ASCII.
-   Copyright (C) 1994, 1995, 1996, 1997 Free Software Foundation, Inc.
+   Copyright (C) 1994, 1995, 1996, 1997, 1998 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -57,4 +57,24 @@ _itoa_word (unsigned long value, char *buflim,
   return bp;
 }
 
+static inline char * __attribute__ ((unused))
+_fitoa_word (unsigned long value, char *buf, unsigned int base, int upper_case)
+{
+  char tmpbuf[sizeof (value) * 4];		/* Worst case length: base 2.  */
+  char *cp = _itoa_word (value, tmpbuf + sizeof (value) * 4, base, upper_case);
+  while (cp < tmpbuf + sizeof (value) * 4)
+    *buf++ = *cp++;
+  return buf;
+}
+
+static inline char * __attribute__ ((unused))
+_fitoa (unsigned long long value, char *buf, unsigned int base, int upper_case)
+{
+  char tmpbuf[sizeof (value) * 4];		/* Worst case length: base 2.  */
+  char *cp = _itoa (value, tmpbuf + sizeof (value) * 4, base, upper_case);
+  while (cp < tmpbuf + sizeof (value) * 4)
+    *buf++ = *cp++;
+  return buf;
+}
+
 #endif	/* itoa.h */
diff --git a/sysdeps/unix/sysv/linux/ttyname.c b/sysdeps/unix/sysv/linux/ttyname.c
index 91f0d7a40f..40b006a8cd 100644
--- a/sysdeps/unix/sysv/linux/ttyname.c
+++ b/sysdeps/unix/sysv/linux/ttyname.c
@@ -26,6 +26,8 @@
 #include <string.h>
 #include <stdlib.h>
 
+#include <stdio-common/_itoa.h>
+
 char *__ttyname = NULL;
 
 static char * getttyname __P ((const char *dev, int fd, dev_t mydev,
@@ -104,6 +106,9 @@ char *
 ttyname (fd)
      int fd;
 {
+  static char *buf;
+  static size_t buflen = 0;
+  char procname[30];
   struct stat st, st1;
   int dostat = 0;
   char *name;
@@ -112,6 +117,23 @@ ttyname (fd)
   if (!__isatty (fd))
     return NULL;
 
+  /* We try using the /proc filesystem.  */
+  *_fitoa_word (fd, __stpcpy (procname, "/proc/self/fd/"), 10, 0) = '\0';
+
+  if (buflen == 0)
+    {
+      buflen = 4095;
+      buf = (char *) malloc (buflen + 1);
+      if (buf == NULL)
+	{
+	  buflen = 0;
+	  return NULL;
+	}
+    }
+
+  if (__readlink (procname, buf, buflen) != -1)
+    return buf;
+
   if (fstat (fd, &st) < 0)
     return NULL;
 
diff --git a/sysdeps/unix/sysv/linux/ttyname_r.c b/sysdeps/unix/sysv/linux/ttyname_r.c
index 9c859caa25..8306cf56c0 100644
--- a/sysdeps/unix/sysv/linux/ttyname_r.c
+++ b/sysdeps/unix/sysv/linux/ttyname_r.c
@@ -26,6 +26,8 @@
 #include <string.h>
 #include <stdlib.h>
 
+#include <stdio-common/_itoa.h>
+
 static int getttyname_r __P ((int fd, char *buf, size_t buflen,
 			      dev_t mydev, ino_t myino, int save,
 			      int *dostat)) internal_function;
@@ -102,6 +104,7 @@ __ttyname_r (fd, buf, buflen)
      char *buf;
      size_t buflen;
 {
+  char procname[30];
   struct stat st, st1;
   int dostat = 0;
   int save = errno;
@@ -127,6 +130,18 @@ __ttyname_r (fd, buf, buflen)
       return ENOTTY;
     }
 
+  /* We try using the /proc filesystem.  */
+  *_fitoa_word (fd, __stpcpy (procname, "/proc/self/fd/"), 10, 0) = '\0';
+
+  ret = __readlink (procname, buf, buflen - 1);
+  if (ret != -1)
+    return 0;
+  if (errno == ENAMETOOLONG)
+    {
+      __set_errno (ERANGE);
+      return ERANGE;
+    }
+
   if (fstat (fd, &st) < 0)
     return errno;