From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: "rusty@rustcorp.com.au" <rusty@rustcorp.com.au>,
"masami.hiramatsu.pt@hitachi.com"
<masami.hiramatsu.pt@hitachi.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
linux-scsi <linux-scsi@vger.kernel.org>
Subject: module: fix module_refcount() return when running in a module exit routine
Date: Sun, 18 Jan 2015 08:55:46 -0800 [thread overview]
Message-ID: <1421600146.2080.8.camel@HansenPartnership.com> (raw)
From: James Bottomley <JBottomley@Parallels.com>
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 <bvanassche@acm.org>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
---
diff --git a/kernel/module.c b/kernel/module.c
index 3965511..c33a113 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -774,7 +774,12 @@ static int try_stop_module(struct module *mod, int flags, int *forced)
unsigned long module_refcount(struct module *mod)
{
- return (unsigned long)atomic_read(&mod->refcnt) - MODULE_REF_BASE;
+ unsigned long ret = atomic_read(&mod->refcnt);
+
+ if (ret == 0)
+ /* ref is already zero (probably in module exit) */
+ return 0;
+ return ret - MODULE_REF_BASE;
}
EXPORT_SYMBOL(module_refcount);
next reply other threads:[~2015-01-18 16:55 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-18 16:55 James Bottomley [this message]
2015-01-18 23:37 ` module: fix module_refcount() return when running in a module exit routine Rusty Russell
2015-01-19 5:18 ` Masami Hiramatsu
2015-01-19 5:51 ` Rusty Russell
2015-01-19 8:28 ` Christoph Hellwig
2015-01-19 16:07 ` James Bottomley
2015-01-19 16:08 ` James Bottomley
2015-01-20 0:45 ` Rusty Russell
2015-01-20 2:17 ` Masami Hiramatsu
2015-01-20 17:23 ` James Bottomley
2015-01-21 5:30 ` Rusty Russell
2015-01-22 16:50 ` Christoph Hellwig
2015-01-22 17:02 ` James Bottomley
2015-01-23 2:54 ` Rusty Russell
2015-01-23 13:17 ` Christoph Hellwig
2015-01-23 18:42 ` James Bottomley
2015-01-23 23:35 ` Rusty Russell
2015-01-26 17:16 ` Christoph Hellwig
2015-01-28 9:23 ` Bart Van Assche
2015-01-28 21:45 ` James Bottomley
2015-01-29 12:16 ` Bart Van Assche
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