Re: (ITS#8339) LMDB robust mutex fix

[hyc@symas.com]

openldap@gulag.ch wrote:
> Hi Hallvard
>
> Thanks for the hint. Your are perfectly right, the mutex memory has to
> be zeroed in case of a robust mutex. Applied against 0.9.18 and it seems
> to work. My proposed patch is broken.

I've pushed a tweaked version of Hallvard's patch. While the Studio compiler 
defines __SunOS_5_10 it appears that gcc doesn't, so we took a different 
detection route.
>
> There is a slight inconsistency if subsequent calls after a successfull
> pthread_mutexattr_init() fail (in the ORed if statement). This might
> result in a memory leak as the mutex attributes are not destroyed. But
> this is not related to the topic of this ITS.

Feel free to submit another ITS for that, thanks.
>
> Thank you
>
> Rolf
>
> On 06/02/16 07:56 AM, Hallvard Breien Furuseth wrote:
>> Rolf, please try this instead, like the manpage you referred to
>> says under Notes.  Do not catch EBUSY/EINVAL, they do mean the
>> mutex was not (re)inited.
>>
>> diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
>> index 0209c09..5ae93bc 100644
>> --- a/libraries/liblmdb/mdb.c
>> +++ b/libraries/liblmdb/mdb.c
>> @@ -304,7 +304,7 @@ union semun {
>>    # else
>>    #  define MDB_USE_ROBUST	1
>>    /* glibc < 2.12 only provided _np API */
>> -#  if defined(__GLIBC__) && GLIBC_VER < 0x02000c
>> +#  if (defined(__GLIBC__) && GLIBC_VER < 0x02000c) || defined(__SunOS_5_10)
>>    #   define PTHREAD_MUTEX_ROBUST	PTHREAD_MUTEX_ROBUST_NP
>>    #   define pthread_mutexattr_setrobust(attr, flag)	pthread_mutexattr_setrobust_np(attr, flag)
>>    #   define pthread_mutex_consistent(mutex)	pthread_mutex_consistent_np(mutex)
>> @@ -4963,6 +4963,13 @@ mdb_env_setup_locks(MDB_env *env, char *lpath, int mode, int *excl)
>>    #else	/* MDB_USE_POSIX_MUTEX: */
>>    		pthread_mutexattr_t mattr;
>>
>> +		/* Solaris needs this before initing a robust mutex.  Otherwise
>> +		 * it may skip the init and return EBUSY "seems someone already
>> +		 * inited" or EINVAL "it was inited differently".
>> +		 */
>> +		memset(env->me_txns->mti_rmutex, 0, sizeof(*env->me_txns->mti_rmutex));
>> +		memset(env->me_txns->mti_wmutex, 0, sizeof(*env->me_txns->mti_wmutex));
>> +
>>    		if ((rc = pthread_mutexattr_init(&mattr))
>>    			|| (rc = pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED))
>>    #ifdef MDB_ROBUST_SUPPORTED
>>
>
>
>
>
>


-- 
   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/