Messages in this thread | | | Date | Mon, 19 Mar 2007 16:34:18 -0700 (PDT) | From | Davide Libenzi <> | Subject | Re: [patch 2/13] signal/timer/event fds v6 - signalfd core ... |
| |
On Tue, 20 Mar 2007, Oleg Nesterov wrote:
> 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.
I did a similar thing, but I renamed the locking functions and its parameters. After looking at what the pid thing was doing, I realized that it was not really needed.
- Davide
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |