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b298d289c7
Commit a144c6a (PM: Print a warning if firmware is requested when tasks
are frozen) introduced usermodehelper_is_disabled() to warn and exit
immediately if firmware is requested when usermodehelpers are disabled.
However, it is racy. Consider the following scenario, currently used in
drivers/base/firmware_class.c:
...
if (usermodehelper_is_disabled())
goto out;
/* Do actual work */
...
out:
return err;
Nothing prevents someone from disabling usermodehelpers just after the check
in the 'if' condition, which means that it is quite possible to try doing the
"actual work" with usermodehelpers disabled, leading to undesirable
consequences.
In particular, this race condition in _request_firmware() causes task freezing
failures whenever suspend/hibernation is in progress because, it wrongly waits
to get the firmware/microcode image from userspace when actually the
usermodehelpers are disabled or userspace has been frozen.
Some of the example scenarios that cause freezing failures due to this race
are those that depend on userspace via request_firmware(), such as x86
microcode module initialization and microcode image reload.
Previous discussions about this issue can be found at:
http://thread.gmane.org/gmane.linux.kernel/1198291/focus=1200591
This patch adds proper synchronization to fix this issue.
It is to be noted that this patchset fixes the freezing failures but doesn't
remove the warnings. IOW, it does not attempt to add explicit synchronization
to x86 microcode driver to avoid requesting microcode image at inopportune
moments. Because, the warnings were introduced to highlight such cases, in the
first place. And we need not silence the warnings, since we take care of the
*real* problem (freezing failure) and hence, after that, the warnings are
pretty harmless anyway.
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
124 lines
3.9 KiB
C
124 lines
3.9 KiB
C
#ifndef __LINUX_KMOD_H__
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#define __LINUX_KMOD_H__
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/*
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* include/linux/kmod.h
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/gfp.h>
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#include <linux/stddef.h>
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#include <linux/errno.h>
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#include <linux/compiler.h>
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#include <linux/workqueue.h>
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#include <linux/sysctl.h>
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#define KMOD_PATH_LEN 256
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#ifdef CONFIG_MODULES
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extern char modprobe_path[]; /* for sysctl */
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/* modprobe exit status on success, -ve on error. Return value
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* usually useless though. */
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extern __printf(2, 3)
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int __request_module(bool wait, const char *name, ...);
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#define request_module(mod...) __request_module(true, mod)
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#define request_module_nowait(mod...) __request_module(false, mod)
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#define try_then_request_module(x, mod...) \
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((x) ?: (__request_module(true, mod), (x)))
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#else
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static inline int request_module(const char *name, ...) { return -ENOSYS; }
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static inline int request_module_nowait(const char *name, ...) { return -ENOSYS; }
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#define try_then_request_module(x, mod...) (x)
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#endif
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struct cred;
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struct file;
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enum umh_wait {
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UMH_NO_WAIT = -1, /* don't wait at all */
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UMH_WAIT_EXEC = 0, /* wait for the exec, but not the process */
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UMH_WAIT_PROC = 1, /* wait for the process to complete */
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};
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struct subprocess_info {
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struct work_struct work;
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struct completion *complete;
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char *path;
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char **argv;
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char **envp;
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enum umh_wait wait;
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int retval;
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int (*init)(struct subprocess_info *info, struct cred *new);
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void (*cleanup)(struct subprocess_info *info);
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void *data;
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};
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/* Allocate a subprocess_info structure */
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struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
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char **envp, gfp_t gfp_mask);
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/* Set various pieces of state into the subprocess_info structure */
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void call_usermodehelper_setfns(struct subprocess_info *info,
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int (*init)(struct subprocess_info *info, struct cred *new),
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void (*cleanup)(struct subprocess_info *info),
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void *data);
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/* Actually execute the sub-process */
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int call_usermodehelper_exec(struct subprocess_info *info, enum umh_wait wait);
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/* Free the subprocess_info. This is only needed if you're not going
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to call call_usermodehelper_exec */
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void call_usermodehelper_freeinfo(struct subprocess_info *info);
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static inline int
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call_usermodehelper_fns(char *path, char **argv, char **envp,
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enum umh_wait wait,
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int (*init)(struct subprocess_info *info, struct cred *new),
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void (*cleanup)(struct subprocess_info *), void *data)
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{
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struct subprocess_info *info;
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gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
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info = call_usermodehelper_setup(path, argv, envp, gfp_mask);
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if (info == NULL)
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return -ENOMEM;
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call_usermodehelper_setfns(info, init, cleanup, data);
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return call_usermodehelper_exec(info, wait);
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}
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static inline int
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call_usermodehelper(char *path, char **argv, char **envp, enum umh_wait wait)
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{
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return call_usermodehelper_fns(path, argv, envp, wait,
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NULL, NULL, NULL);
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}
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extern struct ctl_table usermodehelper_table[];
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extern void usermodehelper_init(void);
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extern int usermodehelper_disable(void);
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extern void usermodehelper_enable(void);
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extern bool usermodehelper_is_disabled(void);
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extern void read_lock_usermodehelper(void);
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extern void read_unlock_usermodehelper(void);
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#endif /* __LINUX_KMOD_H__ */
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