[CRIU] [PATCH RFC 03/30] files: Wait transport_fd before sending a fd to peer

[Kirill Tkhai]

On 08.11.2016 15:54, Pavel Emelyanov wrote:
> On 11/01/2016 05:30 PM, Kirill Tkhai wrote:
>> Now it's excess, because we already wait per-fd transport
>> sockets. But this will be used in next patches.
>>
>> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
>> ---
>>  criu/files.c          |    2 ++
>>  criu/include/pstree.h |    7 +++++++
>>  criu/pstree.c         |    1 +
>>  3 files changed, 10 insertions(+)
>>
>> diff --git a/criu/files.c b/criu/files.c
>> index e869614..97b4e95 100644
>> --- a/criu/files.c
>> +++ b/criu/files.c
>> @@ -964,6 +964,7 @@ int send_fd_to_peer(int fd, struct fdinfo_list_entry *fle, int sock)
>>  
>>  	pr_info("\t\tWait fdinfo pid=%d fd=%d\n", fle->pid, fle->fe->fd);
>>  	futex_wait_while(&fle->real_pid, 0);
>> +	futex_wait_while(&pstree_item_by_virt(fle->pid)->task_st, TSK_ALLOCATED);
> 
> Isn't the wait for fle->real_pid being non zero enough?

Yes, it's excess as written in description ;) The idea is consequentially
to teach the code to use the task_st futex for all waitings. So, this is
one of the steps.
 
>>  	transport_name_gen(&saddr, &len,
>>  			futex_get(&fle->real_pid), fle->fe->fd);
>>  	pr_info("\t\tSend fd %d to %s\n", fd, saddr.sun_path + 1);
>> @@ -1691,6 +1692,7 @@ static int open_transport_socket(pid_t pid)
>>  		return -1;
>>  	}
>>  	close(sock);
>> +	futex_set_and_wake(&current->task_st, TFD_INSTALLED);
>>  
>>  	return 0;
>>  }
>> diff --git a/criu/include/pstree.h b/criu/include/pstree.h
>> index 5768b64..b3547ca 100644
>> --- a/criu/include/pstree.h
>> +++ b/criu/include/pstree.h
>> @@ -4,6 +4,7 @@
>>  #include "common/list.h"
>>  #include "pid.h"
>>  #include "images/core.pb-c.h"
>> +#include "lock.h"
>>  
>>  /*
>>   * That's the init process which usually inherit
>> @@ -24,6 +25,12 @@ struct pstree_item {
>>  	struct pid		*threads;	/* array of threads */
>>  	CoreEntry		**core;
>>  	TaskKobjIdsEntry	*ids;
>> +	futex_t			task_st;
>> +};
>> +
>> +enum {
>> +	TSK_ALLOCATED = 0,
>> +	TFD_INSTALLED = 1 << 0,
>>  };
>>  
>>  struct pstree_item *current;
>> diff --git a/criu/pstree.c b/criu/pstree.c
>> index ec1f7ee..ed7e999 100644
>> --- a/criu/pstree.c
>> +++ b/criu/pstree.c
>> @@ -216,6 +216,7 @@ struct pstree_item *__alloc_pstree_item(bool rst)
>>  	item->pid.virt = -1;
>>  	item->pid.real = -1;
>>  	item->born_sid = -1;
>> +	futex_init(&item->task_st);
>>  
>>  	return item;
>>  }
>>
>> .
>>
>