From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752661AbcHLTcH (ORCPT ); Fri, 12 Aug 2016 15:32:07 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:34597 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751091AbcHLTcG (ORCPT ); Fri, 12 Aug 2016 15:32:06 -0400 Date: Fri, 12 Aug 2016 21:32:01 +0200 From: Ingo Molnar To: Linus Torvalds Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Thomas Gleixner , "Paul E. McKenney" , Andrew Morton Subject: [GIT PULL] locking fixes Message-ID: <20160812193201.GA25424@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Linus, Please pull the latest locking-urgent-for-linus git tree from: git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-urgent-for-linus # HEAD: c2ace36b884de9330c4149064ae8d212d2e0d9ee locking/pvqspinlock: Fix a bug in qstat_read() Misc fixes: lockstat fix, futex fix on !MMU systems, big endian fix for qrwlocks and a race fix for pvqspinlocks. Thanks, Ingo ------------------> Pan Xinhui (1): locking/pvqspinlock: Fix a bug in qstat_read() Thomas Gleixner (1): futex: Assume all mappings are private on !MMU systems Wanpeng Li (1): locking/pvqspinlock: Fix double hash race pan xinhui (1): locking/qrwlock: Fix write unlock bug on big endian systems include/asm-generic/qrwlock.h | 27 +++++++++++++++++++++++++-- kernel/futex.c | 23 ++++++++++++++++++++++- kernel/locking/qspinlock_paravirt.h | 2 +- kernel/locking/qspinlock_stat.h | 1 - 4 files changed, 48 insertions(+), 5 deletions(-) diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h index 54a8e65e18b6..7d026bf27713 100644 --- a/include/asm-generic/qrwlock.h +++ b/include/asm-generic/qrwlock.h @@ -25,7 +25,20 @@ #include /* - * Writer states & reader shift and bias + * Writer states & reader shift and bias. + * + * | +0 | +1 | +2 | +3 | + * ----+----+----+----+----+ + * LE | 78 | 56 | 34 | 12 | 0x12345678 + * ----+----+----+----+----+ + * | wr | rd | + * +----+----+----+----+ + * + * ----+----+----+----+----+ + * BE | 12 | 34 | 56 | 78 | 0x12345678 + * ----+----+----+----+----+ + * | rd | wr | + * +----+----+----+----+ */ #define _QW_WAITING 1 /* A writer is waiting */ #define _QW_LOCKED 0xff /* A writer holds the lock */ @@ -134,12 +147,22 @@ static inline void queued_read_unlock(struct qrwlock *lock) } /** + * __qrwlock_write_byte - retrieve the write byte address of a queue rwlock + * @lock : Pointer to queue rwlock structure + * Return: the write byte address of a queue rwlock + */ +static inline u8 *__qrwlock_write_byte(struct qrwlock *lock) +{ + return (u8 *)lock + 3 * IS_BUILTIN(CONFIG_CPU_BIG_ENDIAN); +} + +/** * queued_write_unlock - release write lock of a queue rwlock * @lock : Pointer to queue rwlock structure */ static inline void queued_write_unlock(struct qrwlock *lock) { - smp_store_release((u8 *)&lock->cnts, 0); + smp_store_release(__qrwlock_write_byte(lock), 0); } /* diff --git a/kernel/futex.c b/kernel/futex.c index 33664f70e2d2..46cb3a301bc1 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -179,7 +179,15 @@ int __read_mostly futex_cmpxchg_enabled; * Futex flags used to encode options to functions and preserve them across * restarts. */ -#define FLAGS_SHARED 0x01 +#ifdef CONFIG_MMU +# define FLAGS_SHARED 0x01 +#else +/* + * NOMMU does not have per process address space. Let the compiler optimize + * code away. + */ +# define FLAGS_SHARED 0x00 +#endif #define FLAGS_CLOCKRT 0x02 #define FLAGS_HAS_TIMEOUT 0x04 @@ -405,6 +413,16 @@ static void get_futex_key_refs(union futex_key *key) if (!key->both.ptr) return; + /* + * On MMU less systems futexes are always "private" as there is no per + * process address space. We need the smp wmb nevertheless - yes, + * arch/blackfin has MMU less SMP ... + */ + if (!IS_ENABLED(CONFIG_MMU)) { + smp_mb(); /* explicit smp_mb(); (B) */ + return; + } + switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { case FUT_OFF_INODE: ihold(key->shared.inode); /* implies smp_mb(); (B) */ @@ -436,6 +454,9 @@ static void drop_futex_key_refs(union futex_key *key) return; } + if (!IS_ENABLED(CONFIG_MMU)) + return; + switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { case FUT_OFF_INODE: iput(key->shared.inode); diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h index 37649e69056c..8a99abf58080 100644 --- a/kernel/locking/qspinlock_paravirt.h +++ b/kernel/locking/qspinlock_paravirt.h @@ -450,7 +450,7 @@ pv_wait_head_or_lock(struct qspinlock *lock, struct mcs_spinlock *node) goto gotlock; } } - WRITE_ONCE(pn->state, vcpu_halted); + WRITE_ONCE(pn->state, vcpu_hashed); qstat_inc(qstat_pv_wait_head, true); qstat_inc(qstat_pv_wait_again, waitcnt); pv_wait(&l->locked, _Q_SLOW_VAL); diff --git a/kernel/locking/qspinlock_stat.h b/kernel/locking/qspinlock_stat.h index 22e025309845..b9d031516254 100644 --- a/kernel/locking/qspinlock_stat.h +++ b/kernel/locking/qspinlock_stat.h @@ -153,7 +153,6 @@ static ssize_t qstat_read(struct file *file, char __user *user_buf, */ if ((counter == qstat_pv_latency_kick) || (counter == qstat_pv_latency_wake)) { - stat = 0; if (kicks) stat = DIV_ROUND_CLOSEST_ULL(stat, kicks); }