Hi, Oleg:
On 10/23/18 12:43 PM, Enke Chen wrote:
>>
>>> --- a/fs/coredump.c
>>> +++ b/fs/coredump.c
>>> @@ -546,6 +546,7 @@ void do_coredump(const kernel_siginfo_t *siginfo)
>>> struct cred *cred;
>>> int retval = 0;
>>> int ispipe;
>>> + bool notify;
>>> struct files_struct *displaced;
>>> /* require nonrelative corefile path and be extra careful */
>>> bool need_suid_safe = false;
>>> @@ -590,6 +591,15 @@ void do_coredump(const kernel_siginfo_t *siginfo)
>>> if (retval < 0)
>>> goto fail_creds;
>>>
>>> + /*
>>> + * Send the pre-coredump signal to the parent if requested.
>>> + */
>>> + read_lock(&tasklist_lock);
>>> + notify = do_notify_parent_predump(current);
>>> + read_unlock(&tasklist_lock);
>>> + if (notify)
>>> + cond_resched();
>>
>> Hmm. I do not understand why do we need cond_resched(). And even if we need it,
>> why we can't call it unconditionally?
>
> Remember the goal is to allow the parent (e.g., a process manager) to take early
> action. The "yield" before doing coredump will help.
>
> The yield is made conditional because the notification is conditional.
> Is that ok?
Given this is in do_coredump(), it is ok to make it unconditional for simplicity.
>>
>>> +bool do_notify_parent_predump(struct task_struct *tsk)
>>> +{
>>> + struct sighand_struct *sighand;
>>> + struct kernel_siginfo info;
>>> + struct task_struct *parent;
>>> + unsigned long flags;
>>> + pid_t pid;
>>> + int sig;
>>> +
>>> + parent = tsk->parent;
>>> + sighand = parent->sighand;
>>> + pid = task_tgid_vnr(tsk);
>>> +
>>> + spin_lock_irqsave(&sighand->siglock, flags);
>>> + sig = parent->signal->predump_signal;
>>> + if (!valid_predump_signal(sig)) {
>>> + spin_unlock_irqrestore(&sighand->siglock, flags);
>>> + return false;
>>> + }
>>
>> Why do we need to check parent->signal->predump_signal under ->siglock?
>> This complicates the code for no reason, afaics.
Will simplify.
Thanks. -- Enke
