From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81649C432C0 for ; Wed, 20 Nov 2019 15:57:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4A10320714 for ; Wed, 20 Nov 2019 15:57:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="R/OI2aqO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732064AbfKTP5g (ORCPT ); Wed, 20 Nov 2019 10:57:36 -0500 Received: from mail-wm1-f73.google.com ([209.85.128.73]:52386 "EHLO mail-wm1-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729198AbfKTP5g (ORCPT ); Wed, 20 Nov 2019 10:57:36 -0500 Received: by mail-wm1-f73.google.com with SMTP id x16so5459991wmk.2 for ; Wed, 20 Nov 2019 07:57:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=KDvfqn9QURm+KEF2yectv0d+1MEDhuQ1dR+OnEQyAsI=; b=R/OI2aqOJID2PpeKdWzROqw3canFAEDDaWXZPjuP5r4HI1DtMo8mpK/dbh8YOe1rK4 0N4pxvRXYJX8TBZRhM/iNzgrmpyIUUuCutogT6J8lJ6hzF2LXIFsbdUTOAREEqXEr7mU TpaUjPmlRTFutGGCRs2K6jg17p+IDvK3XvCWSK6n+ueCgav1Gwh80pxs807Iyqb7HWef 0rVzAXToE2nysrO0yiEJyAdUzjeBbudmwaqK5jXsipZoqsrn6/lJFVSA2akDUFCTQ2Pu DyO4I91iKEV+GiY/11G0alfgrVRg2n443ueay4pS+Rimnd5u3CcNhRHTE06gcXGJsrzx p3dw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=KDvfqn9QURm+KEF2yectv0d+1MEDhuQ1dR+OnEQyAsI=; b=muzmRBOp3OmFdeKq5B5qkhEG7zJO/YkPPEuVQBGChh+eoBfetbBPU5NuAbGjS/nG4u W6pOFdbW52XYq17sBKJSSo9ctHXrzTnXJO4CJSuSk3LfQ+QnHTHBvTyw6kjqMSTLDumH bvep0GK+SYHEPtMFN5dOC6rJZ1TwfOMYjUH4MzhTou1hWOcBKN1zsSDExyzlEv86z8KX LTCpy/tBWm3QTXAd6VAkQ7HF3H2bXB/3vQo58jLMDalN3QFp89WbtShpOT4/PQfnz96t MrpyuL1loIpLOhBaKD+waXZKneKG8xmqw42RGKcKuLnBcJ+6Lq3POY9k8WQngDlp4ort 4gGg== X-Gm-Message-State: APjAAAUa7b8we02ARMyuLJfweFeB4tDnGbTxl8ZSF34Yih1mewwaeLvm XQEmiB2Y/ijBiS6Rq5yTrM+HpNUEIQ== X-Google-Smtp-Source: APXvYqzjvj0OuyZipX3zEcxwwcP46Kfl3Y0SMZPzthCRX+xjarNLAaeDn+HLIVIOgZUI3y2FMtrOjLvSOQ== X-Received: by 2002:adf:ec44:: with SMTP id w4mr4456350wrn.274.1574265453254; Wed, 20 Nov 2019 07:57:33 -0800 (PST) Date: Wed, 20 Nov 2019 16:57:15 +0100 Message-Id: <20191120155715.28089-1-elver@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.24.0.432.g9d3f5f5b63-goog Subject: [PATCH] spinlock_debug: Fix various data races From: Marco Elver To: elver@google.com Cc: peterz@infradead.org, mingo@redhat.com, will@kernel.org, linux-kernel@vger.kernel.org, Qian Cai Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This fixes various data races in spinlock_debug. By testing with KCSAN, it is observable that the console gets spammed with data races reports, suggesting these are extremely frequent. Example data race report: read to 0xffff8ab24f403c48 of 4 bytes by task 221 on cpu 2: debug_spin_lock_before kernel/locking/spinlock_debug.c:85 [inline] do_raw_spin_lock+0x9b/0x210 kernel/locking/spinlock_debug.c:112 __raw_spin_lock include/linux/spinlock_api_smp.h:143 [inline] _raw_spin_lock+0x39/0x40 kernel/locking/spinlock.c:151 spin_lock include/linux/spinlock.h:338 [inline] get_partial_node.isra.0.part.0+0x32/0x2f0 mm/slub.c:1873 get_partial_node mm/slub.c:1870 [inline] write to 0xffff8ab24f403c48 of 4 bytes by task 167 on cpu 3: debug_spin_unlock kernel/locking/spinlock_debug.c:103 [inline] do_raw_spin_unlock+0xc9/0x1a0 kernel/locking/spinlock_debug.c:138 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:159 [inline] _raw_spin_unlock_irqrestore+0x2d/0x50 kernel/locking/spinlock.c:191 spin_unlock_irqrestore include/linux/spinlock.h:393 [inline] free_debug_processing+0x1b3/0x210 mm/slub.c:1214 __slab_free+0x292/0x400 mm/slub.c:2864 As a side-effect, with KCSAN, this eventually locks up the console, most likely due to deadlock, e.g. .. -> printk lock -> spinlock_debug -> KCSAN detects data race -> kcsan_print_report() -> printk lock -> deadlock. This fix will 1) avoid the data races, and 2) allow using lock debugging together with KCSAN. Signed-off-by: Marco Elver Reported-by: Qian Cai --- kernel/locking/spinlock_debug.c | 32 ++++++++++++++++---------------- 1 file changed, 16 insertions(+), 16 deletions(-) diff --git a/kernel/locking/spinlock_debug.c b/kernel/locking/spinlock_debug.c index 399669f7eba8..472dd462a40c 100644 --- a/kernel/locking/spinlock_debug.c +++ b/kernel/locking/spinlock_debug.c @@ -51,19 +51,19 @@ EXPORT_SYMBOL(__rwlock_init); static void spin_dump(raw_spinlock_t *lock, const char *msg) { - struct task_struct *owner = NULL; + struct task_struct *owner = READ_ONCE(lock->owner); - if (lock->owner && lock->owner != SPINLOCK_OWNER_INIT) - owner = lock->owner; + if (owner == SPINLOCK_OWNER_INIT) + owner = NULL; printk(KERN_EMERG "BUG: spinlock %s on CPU#%d, %s/%d\n", msg, raw_smp_processor_id(), current->comm, task_pid_nr(current)); printk(KERN_EMERG " lock: %pS, .magic: %08x, .owner: %s/%d, " ".owner_cpu: %d\n", - lock, lock->magic, + lock, READ_ONCE(lock->magic), owner ? owner->comm : "", owner ? task_pid_nr(owner) : -1, - lock->owner_cpu); + READ_ONCE(lock->owner_cpu)); dump_stack(); } @@ -80,16 +80,16 @@ static void spin_bug(raw_spinlock_t *lock, const char *msg) static inline void debug_spin_lock_before(raw_spinlock_t *lock) { - SPIN_BUG_ON(lock->magic != SPINLOCK_MAGIC, lock, "bad magic"); - SPIN_BUG_ON(lock->owner == current, lock, "recursion"); - SPIN_BUG_ON(lock->owner_cpu == raw_smp_processor_id(), + SPIN_BUG_ON(READ_ONCE(lock->magic) != SPINLOCK_MAGIC, lock, "bad magic"); + SPIN_BUG_ON(READ_ONCE(lock->owner) == current, lock, "recursion"); + SPIN_BUG_ON(READ_ONCE(lock->owner_cpu) == raw_smp_processor_id(), lock, "cpu recursion"); } static inline void debug_spin_lock_after(raw_spinlock_t *lock) { - lock->owner_cpu = raw_smp_processor_id(); - lock->owner = current; + WRITE_ONCE(lock->owner_cpu, raw_smp_processor_id()); + WRITE_ONCE(lock->owner, current); } static inline void debug_spin_unlock(raw_spinlock_t *lock) @@ -99,8 +99,8 @@ static inline void debug_spin_unlock(raw_spinlock_t *lock) SPIN_BUG_ON(lock->owner != current, lock, "wrong owner"); SPIN_BUG_ON(lock->owner_cpu != raw_smp_processor_id(), lock, "wrong CPU"); - lock->owner = SPINLOCK_OWNER_INIT; - lock->owner_cpu = -1; + WRITE_ONCE(lock->owner, SPINLOCK_OWNER_INIT); + WRITE_ONCE(lock->owner_cpu, -1); } /* @@ -187,8 +187,8 @@ static inline void debug_write_lock_before(rwlock_t *lock) static inline void debug_write_lock_after(rwlock_t *lock) { - lock->owner_cpu = raw_smp_processor_id(); - lock->owner = current; + WRITE_ONCE(lock->owner_cpu, raw_smp_processor_id()); + WRITE_ONCE(lock->owner, current); } static inline void debug_write_unlock(rwlock_t *lock) @@ -197,8 +197,8 @@ static inline void debug_write_unlock(rwlock_t *lock) RWLOCK_BUG_ON(lock->owner != current, lock, "wrong owner"); RWLOCK_BUG_ON(lock->owner_cpu != raw_smp_processor_id(), lock, "wrong CPU"); - lock->owner = SPINLOCK_OWNER_INIT; - lock->owner_cpu = -1; + WRITE_ONCE(lock->owner, SPINLOCK_OWNER_INIT); + WRITE_ONCE(lock->owner_cpu, -1); } void do_raw_write_lock(rwlock_t *lock) -- 2.24.0.432.g9d3f5f5b63-goog