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Free all possibly held mutexes in error handlers

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Now that we have 3 mutexes lying around, it's important that we check
and free these if necessary if error() is called in any thread that can
hold them.  To do this, we now have flexthread.c, which defines a
flexthread_mutex struct.  This is a wrapper around a pthread_mutex_t and
a pthread_t.  The idea is that in the error handler, the thread can
check whether it holds the mutex and can free it if and only if it does.
This is important because pthread fast mutexes can be freed by *any*
thread, not just the thread which holds them.

Note: it is only ever safe for a thread to check if it holds the mutex
itself.  It is *never* safe to check if another thread holds a mutex
without first locking that mutex, which makes the whole operation rather
pointless.
This commit is contained in:
Alex Young
2012-07-11 09:43:16 +01:00
parent 17fe6d3023
commit f3f017a87d
17 changed files with 351 additions and 70 deletions
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14
src/control.c
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@@ -205,6 +205,7 @@ void control_serve( struct control * control )
void * control_runner( void * control_uncast )
{
debug("Control thread");
NULLCHECK( control_uncast );
struct control * control = (struct control *)control_uncast;
@@ -313,7 +314,7 @@ int control_mirror(struct control_client* client, int linesc, char** lines)
* one mirror at a time. This is enforced by only accepting a
* single client at a time on the control socket.
*/
flexnbd_switch_lock( flexnbd );
flexnbd_lock_switch( flexnbd );
{
struct server * serve = flexnbd_server(flexnbd);
serve->mirror_super = mirror_super_create(
@@ -333,10 +334,13 @@ int control_mirror(struct control_client* client, int linesc, char** lines)
"Failed to create mirror thread"
);
debug("Control thread mirror super waiting");
enum mirror_state state = mirror_super_wait( serve->mirror_super );
debug("Control thread writing response");
control_write_mirror_response( state, client->socket );
}
flexnbd_switch_unlock( flexnbd );
debug( "Control thread unlocking switch" );
flexnbd_unlock_switch( flexnbd );
debug( "Control thread going away." );
return 0;
@@ -392,6 +396,12 @@ void control_cleanup(struct control_client* client,
int fatal __attribute__ ((unused)) )
{
if (client->socket) { close(client->socket); }
/* This is wrongness */
if ( server_io_locked( client->flexnbd->serve ) ) { server_unlock_io( client->flexnbd->serve ); }
if ( server_acl_locked( client->flexnbd->serve ) ) { server_unlock_acl( client->flexnbd->serve ); }
if ( flexnbd_switch_locked( client->flexnbd ) ) { flexnbd_unlock_switch( client->flexnbd ); }
control_client_destroy( client );
}