[ovs-dev] [threads 06/11] New function ovs_strerror() as a thread-safe replacement for strerror().

Ben Pfaff blp at nicira.com
Wed Jun 19 20:17:07 UTC 2013


Signed-off-by: Ben Pfaff <blp at nicira.com>
---
 configure.ac |    1 +
 lib/util.c   |   48 +++++++++++++++++++++++++++++++++++++-----------
 lib/util.h   |    3 ++-
 3 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/configure.ac b/configure.ac
index 6db4a00..734b2ff 100644
--- a/configure.ac
+++ b/configure.ac
@@ -45,6 +45,7 @@ AC_SEARCH_LIBS([pow], [m])
 AC_SEARCH_LIBS([clock_gettime], [rt])
 AC_SEARCH_LIBS([timer_create], [rt])
 AC_SEARCH_LIBS([pthread_sigmask], [pthread])
+AC_FUNC_STRERROR_R
 
 OVS_CHECK_ESX
 OVS_CHECK_COVERAGE
diff --git a/lib/util.c b/lib/util.c
index 2a06461..6ee8b5c 100644
--- a/lib/util.c
+++ b/lib/util.c
@@ -18,6 +18,7 @@
 #include "util.h"
 #include <errno.h>
 #include <limits.h>
+#include <pthread.h>
 #include <stdarg.h>
 #include <stdint.h>
 #include <stdio.h>
@@ -45,6 +46,9 @@ const char *subprogram_name = "";
 /* --version option output. */
 static char *program_version;
 
+/* Buffer used by ovs_strerror(). */
+DEFINE_PER_THREAD_DATA(struct { char s[128]; }, strerror_buffer, { "" });
+
 void
 ovs_assert_failure(const char *where, const char *function,
                    const char *condition)
@@ -307,19 +311,41 @@ ovs_error_valist(int err_no, const char *format, va_list args)
 const char *
 ovs_retval_to_string(int retval)
 {
-    static char unknown[48];
+    return (!retval ? ""
+            : retval == EOF ? "End of file"
+            : ovs_strerror(retval));
+}
 
-    if (!retval) {
-        return "";
-    }
-    if (retval > 0) {
-        return strerror(retval);
-    }
-    if (retval == EOF) {
-        return "End of file";
+const char *
+ovs_strerror(int error)
+{
+    enum { BUFSIZE = sizeof strerror_buffer_get()->s };
+    int save_errno;
+    char *buffer;
+    char *s;
+
+    save_errno = errno;
+    buffer = strerror_buffer_get()->s;
+
+#if STRERROR_R_CHAR_P
+    /* GNU style strerror_r() might return an immutable static string, or it
+     * might write and return 'buffer', but in either case we can pass the
+     * returned string directly to the caller. */
+    s = strerror_r(error, buffer, BUFSIZE);
+#else  /* strerror_r() returns an int. */
+    s = buffer;
+    if (strerror_r(error, buffer, BUFSIZE)) {
+        /* strerror_r() is only allowed to fail on ERANGE (because the buffer
+         * is too short).  We don't check the actual failure reason because
+         * POSIX requires strerror_r() to return the error but old glibc
+         * (before 2.13) returns -1 and sets errno. */
+        snprintf(buffer, ptb.bufsize, "Unknown error %d", error);
     }
-    snprintf(unknown, sizeof unknown, "***unknown return value: %d***", retval);
-    return unknown;
+#endif
+
+    errno = save_errno;
+
+    return s;
 }
 
 /* Sets global "program_name" and "program_version" variables.  Should
diff --git a/lib/util.h b/lib/util.h
index f5589e3..d7fbe09 100644
--- a/lib/util.h
+++ b/lib/util.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009, 2010, 2011, 2012 Nicira, Inc.
+ * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -213,6 +213,7 @@ void ovs_error(int err_no, const char *format, ...) PRINTF_FORMAT(2, 3);
 void ovs_error_valist(int err_no, const char *format, va_list)
     PRINTF_FORMAT(2, 0);
 const char *ovs_retval_to_string(int);
+const char *ovs_strerror(int);
 void ovs_hex_dump(FILE *, const void *, size_t, uintptr_t offset, bool ascii);
 
 bool str_to_int(const char *, int base, int *);
-- 
1.7.2.5




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