From d89616fda88bc030aaff758d37ede7d35e58841a Mon Sep 17 00:00:00 2001 From: Oleg Drokin Date: Wed, 2 Aug 2017 14:45:16 -0400 Subject: [PATCH] Remove misguided HAVE_MUTEX_OWNER check It is just plain unsafe to peek inside in-kernel mutex structure and make assumptions about what kernel does with those internal fields like owner. Kernel is all too happy to stop doing the expected things like tracing lock owner once you load a tainted module like spl/zfs that is not GPL. As such you will get instant assertion failures like this: VERIFY3(((*(volatile typeof((&((&zo->zo_lock)->m_mutex))->owner) *)& ((&((&zo->zo_lock)->m_mutex))->owner))) == ((void *)0)) failed (ffff88030be28500 == (null)) PANIC at zfs_onexit.c:104:zfs_onexit_destroy() Showing stack for process 3626 CPU: 0 PID: 3626 Comm: mkfs.lustre Tainted: P OE ------------ 3.10.0-debug #1 Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 Call Trace: dump_stack+0x19/0x1b spl_dumpstack+0x44/0x50 [spl] spl_panic+0xbf/0xf0 [spl] zfs_onexit_destroy+0x17c/0x280 [zfs] zfsdev_release+0x48/0xd0 [zfs] Reviewed-by: Brian Behlendorf Reviewed-by: Chunwei Chen Signed-off-by: Oleg Drokin Closes #632 Closes #633 --- config/spl-build.m4 | 30 ------------------------------ include/sys/mutex.h | 10 ---------- 2 files changed, 40 deletions(-) diff --git a/config/spl-build.m4 b/config/spl-build.m4 index 630d67c2d..b2a50bf16 100644 --- a/config/spl-build.m4 +++ b/config/spl-build.m4 @@ -49,7 +49,6 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [ SPL_AC_USLEEP_RANGE SPL_AC_KMEM_CACHE_ALLOCFLAGS SPL_AC_WAIT_ON_BIT - SPL_AC_MUTEX_OWNER SPL_AC_INODE_LOCK SPL_AC_GROUP_INFO_GID SPL_AC_KMEM_CACHE_CREATE_USERCOPY @@ -1562,35 +1561,6 @@ AC_DEFUN([SPL_AC_WAIT_ON_BIT], [ ]) ]) -dnl # -dnl # Check whether mutex has owner with task_struct type. -dnl # -dnl # Note that before Linux 3.0, mutex owner is of type thread_info. -dnl # -dnl # Note that in Linux 3.18, the condition for owner is changed from -dnl # defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_SMP) to -dnl # defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_MUTEX_SPIN_ON_OWNER) -dnl # -AC_DEFUN([SPL_AC_MUTEX_OWNER], [ - AC_MSG_CHECKING([whether mutex has owner]) - tmp_flags="$EXTRA_KCFLAGS" - EXTRA_KCFLAGS="-Werror" - SPL_LINUX_TRY_COMPILE([ - #include - #include - ],[ - DEFINE_MUTEX(m); - struct task_struct *t __attribute__ ((unused)); - t = m.owner; - ],[ - AC_MSG_RESULT(yes) - AC_DEFINE(HAVE_MUTEX_OWNER, 1, [yes]) - ],[ - AC_MSG_RESULT(no) - ]) - EXTRA_KCFLAGS="$tmp_flags" -]) - dnl # dnl # 4.7 API change dnl # i_mutex is changed to i_rwsem. Instead of directly using diff --git a/include/sys/mutex.h b/include/sys/mutex.h index 319235223..d6bd99b4c 100644 --- a/include/sys/mutex.h +++ b/include/sys/mutex.h @@ -40,10 +40,8 @@ typedef enum { typedef struct { struct mutex m_mutex; spinlock_t m_lock; /* used for serializing mutex_exit */ -#ifndef HAVE_MUTEX_OWNER /* only when kernel doesn't have owner */ kthread_t *m_owner; -#endif #ifdef CONFIG_LOCKDEP kmutex_type_t m_type; #endif /* CONFIG_LOCKDEP */ @@ -58,24 +56,16 @@ spl_mutex_set_owner(kmutex_t *mp) * kernel will handle its owner, so we don't need to do anything if it * is defined. */ -#ifndef HAVE_MUTEX_OWNER mp->m_owner = current; -#endif } static inline void spl_mutex_clear_owner(kmutex_t *mp) { -#ifndef HAVE_MUTEX_OWNER mp->m_owner = NULL; -#endif } -#ifdef HAVE_MUTEX_OWNER #define mutex_owner(mp) (ACCESS_ONCE(MUTEX(mp)->owner)) -#else -#define mutex_owner(mp) (ACCESS_ONCE((mp)->m_owner)) -#endif #define mutex_owned(mp) (mutex_owner(mp) == current) #define MUTEX_HELD(mp) mutex_owned(mp) #define MUTEX_NOT_HELD(mp) (!MUTEX_HELD(mp)) -- 2.40.0