Re: Help with apr mutex
Why not check the return status of the lock and unlock calls??
On Feb 28, 2011, at 12:26 PM, Simone Caruso wrote:
Hi all,
I wrote a simple cache inside my module with apr_shm and apr_rmm, but I have
problems with apr mutex...
I have this peace of code:
static apr_global_mutex_t *mtx = NULL;
static void module_translate_name(request_rec *r)
{
if(apr_global_mutex_trylock(mtx) == APR_EBUSY)
ap_log_rerror(APLOG_MARK, APLOG_WARNING|APLOG_NOERRNO, 0, r,
Memory Locked!! );
apr_global_mutex_lock(mtx);
element = get_from_cache();
if(element == NULL){
element = insert_into_cache();
strcpy(element.name,name\0);
}
apr_global_mutex_unlock(mtx);
}
static void module_post_config(apr_pool_t *p, apr_pool_t *plog, apr_pool_t
*ptemp, server_rec *s)
{
result = apr_global_mutex_create(mtx, cache_entries_lck,
APR_LOCK_DEFAULT, p);
}
static void mod_vhost_ldap_child_init(apr_pool_t * p, server_rec * s)
{
apr_status_t ret;
ret = apr_global_mutex_child_init(mtx, cache_entries_lck, p);
}
During my tests with 'ab -c 15 -n 3000' i NEVER get the Memory Locked error
in logs, plus i get duplicated entries in cache but I don't know why!
Does someone have an idea? (please consider i use apr_global_mutex_trylock()
only for test)
Regards.
--
Simone Caruso
Re: Help with apr mutex
a few things to try:
* you should use APR_STATUS_IS_EBUSY(s) instead of ... == APR_EBUSY
* after creating the mutex, you might have to set permissions on it:
#ifdef AP_NEED_SET_MUTEX_PERMS
rc = unixd_set_global_mutex_perms(mutex);
if(rc != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_CRIT, rc, s, Could not set
permissions on global parent mutex %s, mutex_name);
return rc;
}
#endif
* I *think* that calling the lock functions twice from a same thread
(without unlocking first) can have undefined behavior, i.e. don't do
the lock() just after the trylock() call.
regards,
thomas
On Mon, Feb 28, 2011 at 18:26, Simone Caruso i...@simonecaruso.com wrote:
Hi all,
I wrote a simple cache inside my module with apr_shm and apr_rmm, but I have
problems with apr mutex...
I have this peace of code:
static apr_global_mutex_t *mtx = NULL;
static void module_translate_name(request_rec *r)
{
if(apr_global_mutex_trylock(mtx) == APR_EBUSY)
ap_log_rerror(APLOG_MARK, APLOG_WARNING|APLOG_NOERRNO, 0, r,
Memory Locked!! );
apr_global_mutex_lock(mtx);
element = get_from_cache();
if(element == NULL){
element = insert_into_cache();
strcpy(element.name,name\0);
}
apr_global_mutex_unlock(mtx);
}
static void module_post_config(apr_pool_t *p, apr_pool_t *plog, apr_pool_t
*ptemp, server_rec *s)
{
result = apr_global_mutex_create(mtx, cache_entries_lck,
APR_LOCK_DEFAULT, p);
}
static void mod_vhost_ldap_child_init(apr_pool_t * p, server_rec * s)
{
apr_status_t ret;
ret = apr_global_mutex_child_init(mtx, cache_entries_lck, p);
}
During my tests with 'ab -c 15 -n 3000' i NEVER get the Memory Locked
error in logs, plus i get duplicated entries in cache but I don't know why!
Does someone have an idea? (please consider i use apr_global_mutex_trylock()
only for test)
Regards.
--
Simone Caruso
Re: Help with apr mutex
On 28/02/2011 18:35, Jim Jagielski wrote:
Why not check the return status of the lock and unlock calls??
Ehm... i'm an idiot...
i create the lock in this way:
module_post_config(apr_pool_t *p, apr_pool_t *plog, apr_pool_t *ptemp,
server_rec *s)
{
lock = ap_server_root_relative(p, mymod.lck);
result = apr_global_mutex_create(mtx, lock, APR_LOCK_DEFAULT, p);
if(result != APR_SUCCESS)
...
}
apr_global_mutex_create returns APR_SUCCESS, but apr_global_mutex_lock returns
Permission denied,
maybe the lock is created wrong permissions ??
--
Simone Caruso
IT Consultant
Re: Help with apr mutex
On 28/02/2011 18:53, thomas bonfort wrote:
a few things to try:
* you should use APR_STATUS_IS_EBUSY(s) instead of ... == APR_EBUSY
* after creating the mutex, you might have to set permissions on it:
#ifdef AP_NEED_SET_MUTEX_PERMS
rc = unixd_set_global_mutex_perms(mutex);
if(rc != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_CRIT, rc, s, Could not set
permissions on global parent mutex %s, mutex_name);
return rc;
}
#endif
* I *think* that calling the lock functions twice from a same thread
(without unlocking first) can have undefined behavior, i.e. don't do
the lock() just after the trylock() call.
regards,
thomas
Thanks Thoms,
i'm going to try your code!
--
Simone Caruso
IT Consultant
+39 349 65 90 805
p.iva: 03045250838
Re: Help with apr mutex
On Mon, Feb 28, 2011 at 18:26, Simone Caruso i...@simonecaruso.com wrote: I wrote a simple cache inside my module with apr_shm and apr_rmm Simone, have a look at ap_socache.h and ap_slotmem.h, they're two simple cache facilities that were added in 2.3.0. Might save you some work. :)
