Messages in this thread | | | Date | Tue, 20 Mar 2007 02:28:42 +0300 | From | Oleg Nesterov <> | Subject | Re: [patch 2/13] signal/timer/event fds v6 - signalfd core ... |
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On 03/20, Oleg Nesterov wrote: > > On 03/19, Davide Libenzi wrote: > > > > I'd need a get_task_struct in any case in order to safely call > > unlock_task_sighand(). At that point I'd prefer to just pass through the > > struct pid*. I'll be posting the new version for review as soon as I > > complete a few tests ... > > If signalfd_get_sighand()->lock_task_sighand() succeeds, it is safe to > dereference ctx->tsk. The task can't be freed and ctx->tsk can't be cleared > while we are holding siglock. > > However, I was wrong, we still need a re-check after lock_task_sighand(). > We should check ctx->tsk != NULL.
IOW, we can (afaics) do
static struct sighand_struct *signalfd_get_sighand(struct signalfd_ctx *ctx, unsigned long *flags) { struct sighand_struct *sighand = NULL; struct tsak_struct *tsk;
rcu_read_lock(); tsk = rcu_dereference(ctx->tsk); // not needed, just a documentation if (tsk != NULL) sighand = lock_task_sighand(tsk, flags); rcu_read_unlock();
if (sighand && !ctx->tsk)) { unlock_task_sighand(tsk, flags); sighand = NULL; }
return sighand; }
If signalfd_get_sighand() succeeds, ctx->tsk is pinned.
Oleg.
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