[CRIU] [PATCH 7/8] sig: Optimize sigactions restore

[Pavel Emelyanov]

On 08/06/2014 05:01 PM, Andrew Vagin wrote:
> On Wed, Aug 06, 2014 at 04:25:38PM +0400, Pavel Emelyanov wrote:
>> Most of the sigactions are the same across the tasks in the image.
>> Nonetheless existing code always calls a syscall to restore them 
>> and spends 64 calls per-task.
>>
>> Let's restore signals before forking children and let them inherit
>> sigactions. Tune one only if it differs from the parent's.
> 
> I like the idea. Do we have test, which uses different signal actions
> for parent and child?

All timers tests are such. The pdeath_sig one is. The file_fown.

>>
>> Signed-off-by: Pavel Emelyanov <xemul at parallels.com>
>> ---
>>  cr-restore.c | 32 ++++++++++++++++++++++++++++----
>>  1 file changed, 28 insertions(+), 4 deletions(-)
>>
>> diff --git a/cr-restore.c b/cr-restore.c
>> index afdafd8..0408aa3 100644
>> --- a/cr-restore.c
>> +++ b/cr-restore.c
>> @@ -614,6 +614,22 @@ static int open_vmas(int pid)
>>  }
>>  
>>  static rt_sigaction_t sigchld_act;
>> +static rt_sigaction_t parent_act[SIGMAX];
>> +
>> +static bool sa_inherited(int sig, rt_sigaction_t *sa)
>> +{
>> +	rt_sigaction_t *pa;
>> +
>> +	if (current == root_item)
>> +		return false; /* XXX -- inherit from CRIU? */
>> +
>> +	pa = &parent_act[sig];
>> +	return pa->rt_sa_handler == sa->rt_sa_handler &&
>> +		pa->rt_sa_flags == sa->rt_sa_flags &&
>> +		pa->rt_sa_restorer == sa->rt_sa_restorer &&
>> +		pa->rt_sa_mask.sig[0] == sa->rt_sa_mask.sig[0];
>> +}
>> +
>>  static int prepare_sigactions(void)
>>  {
>>  	int pid = current->pid.virt;
>> @@ -621,7 +637,7 @@ static int prepare_sigactions(void)
>>  	int fd_sigact;
>>  	SaEntry *e;
>>  	int sig;
>> -	int ret = -1;
>> +	int ret = 0;
>>  
>>  	fd_sigact = open_image(CR_FD_SIGACT, O_RSTR, pid);
>>  	if (fd_sigact < 0)
>> @@ -655,6 +671,10 @@ static int prepare_sigactions(void)
>>  			sigchld_act = act;
>>  			continue;
>>  		}
>> +
>> +		if (sa_inherited(sig, &act))
>> +			continue;
>> +
>>  		/*
>>  		 * A pure syscall is used, because glibc
>>  		 * sigaction overwrites se_restorer.
>> @@ -664,6 +684,8 @@ static int prepare_sigactions(void)
>>  			pr_err("%d: Can't restore sigaction: %m\n", pid);
>>  			goto err;
>>  		}
>> +
>> +		parent_act[sig] = act;
>>  	}
>>  
>>  err:
>> @@ -716,9 +738,6 @@ static int restore_one_alive_task(int pid, CoreEntry *core)
>>  	if (prepare_file_locks(pid))
>>  		return -1;
>>  
>> -	if (prepare_sigactions())
>> -		return -1;
>> -
>>  	if (open_vmas(pid))
>>  		return -1;
>>  
>> @@ -1346,6 +1367,9 @@ static int restore_task_with_children(void *_arg)
>>  	if (prepare_task_cgroup(current) < 0)
>>  		return -1;
>>  
>> +	if (prepare_sigactions() < 0)
>> +		return -1;
>> +
>>  	if (create_children_and_session())
>>  		goto err;
>>  
>> -- 
>> 1.8.4.2
>>
>>
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> .
>