Hello.
I've written a multi-threaded puller for getting a lot of SNMP data.
When the application do pulling I see the messages:
_callback_lock already locket in snmp_call_callbacks
netsnmp_assert 1==_locks[major][minor] failed callback.c:126
_callback_lock()
Looking at callback.c I've found a function _callback_lock() very
primitive. It does not wait if a lock exists, just returns with the
messages above. (Pleas, note a type: locket -> locked).
I've add a simple waiting loop and messages gone. A patch in an
attachment. I do no magic with autoconf and includes is not enveloped
with #if. May be somebody can do this work?
And I should note, operations with locks as integer array is not atomic
at all! So some problems with multi-threads may rise anyway.
--
Sem.
--- snmplib/callback.c.orig 2007-02-05 14:01:43.000000000 +0300
+++ snmplib/callback.c 2008-01-18 19:08:17.000000000 +0300
@@ -38,6 +38,9 @@
#include <dmalloc.h>
#endif
+#include <sys/socket.h>
+#include <sys/time.h>
+
#include <net-snmp/types.h>
#include <net-snmp/output_api.h>
#include <net-snmp/utilities.h>
@@ -107,6 +110,9 @@
NETSNMP_STATIC_INLINE int
_callback_lock(int major, int minor, const char* warn, int assert)
{
+ int n=0;
+ struct timeval lock_time = { 0, 1000 };
+
#ifdef NETSNMP_PARANOID_LEVEL_HIGH
if (major >= MAX_CALLBACK_IDS || minor >= MAX_CALLBACK_SUBIDS) {
netsnmp_assert("bad callback id");
@@ -119,18 +125,23 @@
types[major], (SNMP_CALLBACK_LIBRARY == major) ?
SNMP_STRORNULL(lib[minor]) : "null"));
#endif
- if (CALLBACK_LOCK(major,minor) > 1)
+ while (CALLBACK_LOCK_COUNT(major,minor) >= 1 && ++n < 100)
+ select(0, NULL, NULL, NULL, &lock_time);
+
+ if(n >= 100)
{
if (NULL != warn)
snmp_log(LOG_WARNING,
- "_callback_lock already locket in %s\n", warn);
- if (assert)
- netsnmp_assert(1==CALLBACK_LOCK_COUNT(major,minor));
+ "lock in _callback_lock sleeps more than 100 microseconds
in %s\n", warn);
+/* if (assert)
+ netsnmp_assert(1==CALLBACK_LOCK_COUNT(major,minor));*/
return 1;
}
- else
+ else {
+ CALLBACK_LOCK(major,minor);
return 0;
+ }
}
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