Messages in this thread | | | Date | Mon, 19 Mar 2007 23:36:15 +0300 | From | Oleg Nesterov <> | Subject | Re: [patch 2/13] signal/timer/event fds v6 - signalfd core ... |
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On 03/19, Davide Libenzi wrote: > > On Mon, 19 Mar 2007, Eric W. Biederman wrote: > > > > +struct signalfd_ctx { > > > + struct list_head lnk; > > > + wait_queue_head_t wqh; > > > + sigset_t sigmask; > > > + struct task_struct *tsk; > > > +}; > > > > I think you want to use a struct pid *pid instead of a pointer to the > > task struct here. It is slightly less efficient (one more > > dereference) but it means that we won't pin the task struct in memory > > indefinitely. Pinning the task_struct like this makes for a very > > interesting way to get around the limits on the number of processes a > > user can have. > > Hmm, when the task is detached from the sighand, we get a notify, so I > could do a put from there. This would avoid the extra de-reference. I need > to verify locking though ...
In that case (if I understand you correctly) we don't need {get,put}_task_struct() at all.
signalfd_deliver(-1) sets ctx->tsk = NULL, signalfd_get_sighand() reads ->tsk under rcu_read_lock(). The code becomes even simpler, we don't need to check list_empty(&ctx->lnk).
Oleg.
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