Re: ipv6: tunnel: hang when destroying ipv6 tunnel
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: 2012-04-01 03:22:49
Also in:
lkml
Subsystem:
module support, the rest · Maintainers:
Luis Chamberlain, Petr Pavlu, Daniel Gomez, Sami Tolvanen, Linus Torvalds
Sasha Levin wrote:
While it seems that 9p is the culprit, I have to point out that this bug is easily reproducible, and it happens each time due to a call_usermode_helper() call. Other than that 9p behaves perfectly and I'd assume that I'd be seeing other things break besides call_usermode_helper() related ones.
I think one of below two patches can catch the bug if this is a usermodehelper related bug. Please try. ----- Patch 1 -----
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 01394b6..3e63319 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c@@ -571,7 +571,7 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait) * flag, for khelper thread is already waiting for the thread at * wait_for_completion() in do_fork(). */ - if (wait != UMH_NO_WAIT && current == kmod_thread_locker) { + if (WARN_ON(wait != UMH_NO_WAIT && current == kmod_thread_locker)) { retval = -EBUSY; goto out; } ----- Patch 2 -----
diff --git a/include/linux/kmod.h b/include/linux/kmod.h
index 9efeae6..1350670 100644
--- a/include/linux/kmod.h
+++ b/include/linux/kmod.h@@ -48,10 +48,10 @@ static inline int request_module_nowait(const char *name, ...) { return -ENOSYS; struct cred; struct file; -#define UMH_NO_WAIT 0 /* don't wait at all */ -#define UMH_WAIT_EXEC 1 /* wait for the exec, but not the process */ -#define UMH_WAIT_PROC 2 /* wait for the process to complete */ -#define UMH_KILLABLE 4 /* wait for EXEC/PROC killable */ +#define UMH_NO_WAIT 0x10 /* don't wait at all */ +#define UMH_WAIT_EXEC 0x11 /* wait for the exec, but not the process */ +#define UMH_WAIT_PROC 0x12 /* wait for the process to complete */ +#define UMH_KILLABLE 0x04 /* wait for EXEC/PROC killable */ struct subprocess_info { struct work_struct work;
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 957a7aa..ecfd3d5 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c@@ -483,6 +483,18 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait) DECLARE_COMPLETION_ONSTACK(done); int retval = 0; + if (unlikely(wait == -1 || wait == 0 || wait == 1)) { + WARN(1, "Requesting for usermode helper with hardcoded wait " + "flag. Change to use UMH_* symbols and recompile, or " + "this request will fail on Linux 3.4.\n"); + if (wait == -1) + wait = UMH_NO_WAIT; + else if (wait == 0) + wait = UMH_WAIT_EXEC; + else + wait = UMH_WAIT_PROC; + } + helper_lock(); if (sub_info->path[0] == '\0') goto out;