linux-kernel - Re: [PATCH V2] UBI: add ubi_lnum_purge function to clear work queue for a lnum

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.00.1205191140280.19017@eristoteles.iwoars.net>
Date:	Sat, 19 May 2012 11:46:58 +0200 (CEST)
From:	Joel Reardon <joel@...mbassador.com>
To:	Artem Bityutskiy <dedekind1@...il.com>
cc:	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] UBI: add ubi_lnum_purge function to clear work queue
 for a lnum

> Take the work_sem at the beginning. Release at the very end.
>
> Then you can do something like this:
>
> int found = 1;
>
> while (found) {
> 	found = 0;
>
> 	spin_lock(&ubi->wl_lock);
> 	list_for_each_entry(wrk, tmp, &ubi->works, list) {
> 		if (wrk->lnum == lnum) {
> 			list_del(&wrk->list);
> 			ubi->works_count -= 1;
> 			ubi_assert(ubi->works_count >= 0);
> 			spin_unlock(&ubi->wl_lock);
>
> 			err = wrk->func(ubi, wrk, 0);
> 			if (err)
> 				return err;
>
> 			spin_lock(&ubi->wl_lock);
> 			found = 1;
> 			break;
> 	}
> 	spin_unlock(&ubi->wl_lock);
> }
>


If I use list_for_each_entry_safe(), it protects against deleting as it
iterates. If I take the work_sem first, is it okay to do a simple
traversal instead of one traversal per removed item? Even if another
thread adds new work for the same vol_id/lnum, its okay, because the
caller of this function only cares about vol_id/lnums erasures that
it knows are currently on the worklist.

Cheers,
Joel Reardon
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/