Messages in this thread Patch in this message | | | Date | Mon, 12 Apr 2004 10:25:49 -0500 | From | Brian King <> | Subject | Re: [PATCH] call_usermodehelper hang |
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Andrew Morton wrote: > Greg KH <greg@kroah.com> wrote: > >>>The deadlock opportunity occurs during the call_usermodehelper() handoff to >> >> > keventd, which is synchronous. >> > >> > 2-3 years back I did have a call_usermodehelper() which was fully async. >> > It was pretty unpleasant because of the need to atomically allocate >> > arbitrary amounts of memory to hold the argv[] and endp[] arrays, to pass >> > them between a couple of threads and to then correctly free it all up >> > again. >> >> Ok, you've convinced me of the mess that would cause. So what should we >> do to help fix this? Serialize call_usermodehelper()? > > > May as well bring back call_usermodehelper_async() I guess. > > > There are two patches here, and they are totally untested...
I loaded the patches on my ppc64 box and they worked fine after I fixed a compile bug. The attached patch fixes the compile bug and changes the call_usermodehelper call in kset_hotplug to call_usermodehelper_async.
-Brian
-- Brian King eServer Storage I/O IBM Linux Technology Center
Fixes a compile error in call_usermodehelper_async and changes kset_hotplug to use call_usermodehelper_async, since it is called with a semaphore held, which can result in a deadlock.
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diff -puN kernel/kmod.c~call_usermodehelper_kobject kernel/kmod.c --- linux-2.6.5/kernel/kmod.c~call_usermodehelper_kobject Mon Apr 12 08:27:20 2004 +++ linux-2.6.5-bjking1/kernel/kmod.c Mon Apr 12 08:27:44 2004 @@ -296,7 +296,7 @@ int call_usermodehelper_async(char *path { struct subprocess_info *sub_info; - if (system_state != SYSTEM_RUNNING) + if (!system_running) return -EBUSY; if (path[0] == '\0') goto out; diff -puN lib/kobject.c~call_usermodehelper_kobject lib/kobject.c --- linux-2.6.5/lib/kobject.c~call_usermodehelper_kobject Mon Apr 12 08:28:07 2004 +++ linux-2.6.5-bjking1/lib/kobject.c Mon Apr 12 08:28:28 2004 @@ -187,7 +187,7 @@ static void kset_hotplug(const char *act pr_debug ("%s: %s %s %s %s %s %s %s\n", __FUNCTION__, argv[0], argv[1], envp[0], envp[1], envp[2], envp[3], envp[4]); - retval = call_usermodehelper (argv[0], argv, envp, 0); + retval = call_usermodehelper_async (argv[0], argv, envp, GFP_KERNEL); if (retval) pr_debug ("%s - call_usermodehelper returned %d\n", __FUNCTION__, retval); _
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