From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752349AbbASQIY (ORCPT ); Mon, 19 Jan 2015 11:08:24 -0500 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:51884 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751396AbbASQIX (ORCPT ); Mon, 19 Jan 2015 11:08:23 -0500 Message-ID: <1421683701.2080.25.camel@HansenPartnership.com> Subject: Re: module: fix module_refcount() return when running in a module exit routine From: James Bottomley To: Rusty Russell Cc: Masami Hiramatsu , linux-kernel , linux-scsi Date: Mon, 19 Jan 2015 08:08:21 -0800 In-Reply-To: <878ugzco8c.fsf@rustcorp.com.au> References: <1421600146.2080.8.camel@HansenPartnership.com> <54BC93C3.7010808@hitachi.com> <878ugzco8c.fsf@rustcorp.com.au> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.7 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2015-01-19 at 16:21 +1030, Rusty Russell wrote: > Masami Hiramatsu writes: > > (2015/01/19 1:55), James Bottomley wrote: > >> From: James Bottomley > >> > >> After e513cc1 module: Remove stop_machine from module unloading, > >> module_refcount() is returning (unsigned long)-1 when called from within > >> a routine that runs in module_exit. This is confusing the scsi device > >> put code which is coded to detect a module_refcount() of zero for > >> running within a module exit routine and not try to do another > >> module_put. The fix is to restore the original behaviour of > >> module_refcount() and return zero if we're running inside an exit > >> routine. > >> > >> Fixes: e513cc1c07e2ab93a4514eec9833e031df3e30bb > >> Reported-by: Bart Van Assche > >> Signed-off-by: James Bottomley > >> > > > > Yes, this should be fixed as you said, since it must return "unsigned long" value. > > But there are only three non-module callers: > > drivers/scsi/scsi.c:1012: if (module && module_refcount(module) != 0) > drivers/staging/lustre/lustre/obdclass/lu_object.c:1359: LINVRNT(module_refcount(key->lct_owner) > 0); > include/linux/module.h:447:unsigned long module_refcount(struct module *mod); > kernel/debug/kdb/kdb_main.c:2026: kdb_printf("%4ld ", module_refcount(mod)); > kernel/module.c:775:unsigned long module_refcount(struct module *mod) > kernel/module.c:779:EXPORT_SYMBOL(module_refcount); > kernel/module.c:859: seq_printf(m, " %lu ", module_refcount(mod)); > kernel/module.c:911: return sprintf(buffer, "%lu\n", module_refcount(mk->mod)); > > The first one I think should be eliminated, and the second one is simply > an assertion before calling module_put() (which should probably be > eliminated). The others are just printing information. If you really want to insist on module_reference() returning -1 when the module is in it's exit phase, OK, but in that case, I think it should return a signed value, not an unsigned one. James