From patchwork Thu Nov 26 20:39:54 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Adhemerval Zanella X-Patchwork-Id: 41196 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 5C4DC383303E; Thu, 26 Nov 2020 20:40:03 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 5C4DC383303E DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1606423203; bh=bn3RrKEetONQWgBq2h37arD9PvIg8teB8VTWGwBU+Oo=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=Ny+kbY0vZgAzCPdSEH+BdOmt/hDBQroCOKVk+c3eS9TL7OEDOdH7ASAW8bszu8QpN kAmjQvzj+Vs0MkOghOJPU68irKfgPvAd1I+jIeRU9LAXS9aOnlTXPvw0LvP2Do7Lhr Cfz4fzssDluNE9i2YX1/0rUxFqoXpFHb5Sg5SN74= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mail-qv1-xf30.google.com (mail-qv1-xf30.google.com [IPv6:2607:f8b0:4864:20::f30]) by sourceware.org (Postfix) with ESMTPS id 3AB1A3851C01 for ; Thu, 26 Nov 2020 20:40:00 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 3AB1A3851C01 Received: by mail-qv1-xf30.google.com with SMTP id 4so1463064qvh.1 for ; Thu, 26 Nov 2020 12:40:00 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=bn3RrKEetONQWgBq2h37arD9PvIg8teB8VTWGwBU+Oo=; b=TJVfMt0ywNZhLFtRAS8GgGL3YSBE289QOZJg5KOpO6/Hs4k5k2EI1FPnc5CKGvcX2Q X52d7pjLxowfatc/+4VLK7Um0loZ6Dkgyh6LpYRMsTvxJ38SxI8W+8xrKo0Z94IR8Cj2 6tzLs3gFc7vMzmaYGjKQZzuHm8cTjQ3xKmiInpxH3WGSojiVAmWozwHlA9CQFI0dr88g ExhhxgqmTuXJz1aV2nRbF7/6Y+Csig4fkyDTxamg7/W+ayWqcgVLYHBdY9HUYZzt4GgP uh26z4K1RXHWWwmW+Z2nSDbzGzxXkf7txoUXWJAz0Xc81S8EQA0XTjMf6glRnZDp+CFW spag== X-Gm-Message-State: AOAM530luShUaelhLe62Lg30az5ahTkVMukel0t1B4h6jZLJMwBLHXdZ T2IvmHQcYIgoO2HazAaKSJZJnasCjSIELA== X-Google-Smtp-Source: ABdhPJye2ASkiYOAoVJ1hKb67/A2HHQlV+6HPwCQKUiW+IUWKyVI2F1bFWuxKMwRgCL+QD7DbWtm6A== X-Received: by 2002:ad4:468b:: with SMTP id bq11mr4949399qvb.8.1606423199598; Thu, 26 Nov 2020 12:39:59 -0800 (PST) Received: from localhost.localdomain ([177.194.48.209]) by smtp.googlemail.com with ESMTPSA id m8sm3863524qkn.41.2020.11.26.12.39.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Nov 2020 12:39:59 -0800 (PST) To: libc-alpha@sourceware.org, Mike Crowe Subject: [PATCH] nptl: Add EOVERFLOW checks for futex calls Date: Thu, 26 Nov 2020 17:39:54 -0300 Message-Id: <20201126203954.443334-1-adhemerval.zanella@linaro.org> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Spam-Status: No, score=-13.8 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Adhemerval Zanella via Libc-alpha From: Adhemerval Zanella Reply-To: Adhemerval Zanella Cc: Michael Kerrisk Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" Some futex-internal calls require additional check for EOVERFLOW (as indicated by [1] [2]). For both mutex and rwlock code, EOVERFLOW is handle as ETIMEDOUT; since it indicate to the caller that the blocking operation could not be performed. For mutex it avoids a possible issue where PTHREAD_MUTEX_ROBUST_* might assume EOVERFLOW indicate futex has succeed, and for PTHREAD_MUTEX_PP_* it avoid a potential busy infinite loop. For rwlock, is also avoid potential busy infinite loops. Checked on x86_64-linux-gnu and i686-linux-gnu, although EOVERFLOW won't be possible with current usage (since all timeouts on 32-bit architectures with 32-bit time_t support will be in the range of 32-bit time_t). [1] https://sourceware.org/pipermail/libc-alpha/2020-November/120079.html [2] https://sourceware.org/pipermail/libc-alpha/2020-November/120080.html --- nptl/pthread_mutex_timedlock.c | 6 +++--- nptl/pthread_rwlock_common.c | 14 +++++++------- 2 files changed, 10 insertions(+), 10 deletions(-) diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c index 74adffe790..6c72a36b2b 100644 --- a/nptl/pthread_mutex_timedlock.c +++ b/nptl/pthread_mutex_timedlock.c @@ -270,7 +270,7 @@ __pthread_mutex_clocklock_common (pthread_mutex_t *mutex, oldval, clockid, abstime, PTHREAD_ROBUST_MUTEX_PSHARED (mutex)); /* The futex call timed out. */ - if (err == ETIMEDOUT) + if (err == ETIMEDOUT || err == EOVERFLOW) return err; /* Reload current lock value. */ oldval = mutex->__data.__lock; @@ -550,8 +550,8 @@ __pthread_mutex_clocklock_common (pthread_mutex_t *mutex, int e = __futex_abstimed_wait64 ( (unsigned int *) &mutex->__data.__lock, ceilval | 2, clockid, abstime, PTHREAD_MUTEX_PSHARED (mutex)); - if (e == ETIMEDOUT) - return ETIMEDOUT; + if (e == ETIMEDOUT || e == EOVERFLOW) + return e; } } while (atomic_compare_and_exchange_val_acq (&mutex->__data.__lock, diff --git a/nptl/pthread_rwlock_common.c b/nptl/pthread_rwlock_common.c index 4c9f582d3d..9ef432c474 100644 --- a/nptl/pthread_rwlock_common.c +++ b/nptl/pthread_rwlock_common.c @@ -334,7 +334,7 @@ __pthread_rwlock_rdlock_full64 (pthread_rwlock_t *rwlock, clockid_t clockid, private); /* We ignore EAGAIN and EINTR. On time-outs, we can just return because we don't need to clean up anything. */ - if (err == ETIMEDOUT) + if (err == ETIMEDOUT || err == EOVERFLOW) return err; } /* It makes sense to not break out of the outer loop here @@ -460,7 +460,7 @@ __pthread_rwlock_rdlock_full64 (pthread_rwlock_t *rwlock, clockid_t clockid, int err = __futex_abstimed_wait64 (&rwlock->__data.__wrphase_futex, 1 | PTHREAD_RWLOCK_FUTEX_USED, clockid, abstime, private); - if (err == ETIMEDOUT) + if (err == ETIMEDOUT || err == EOVERFLOW) { /* If we timed out, we need to unregister. If no read phase has been installed while we waited, we can just decrement @@ -479,7 +479,7 @@ __pthread_rwlock_rdlock_full64 (pthread_rwlock_t *rwlock, clockid_t clockid, if (atomic_compare_exchange_weak_relaxed (&rwlock->__data.__readers, &r, r - (1 << PTHREAD_RWLOCK_READER_SHIFT))) - return ETIMEDOUT; + return err; /* TODO Back-off. */ } /* Use the acquire MO fence to mirror the steps taken in the @@ -730,7 +730,7 @@ __pthread_rwlock_wrlock_full64 (pthread_rwlock_t *rwlock, clockid_t clockid, int err = __futex_abstimed_wait64 (&rwlock->__data.__writers_futex, 1 | PTHREAD_RWLOCK_FUTEX_USED, clockid, abstime, private); - if (err == ETIMEDOUT) + if (err == ETIMEDOUT || err == EOVERFLOW) { if (prefer_writer) { @@ -758,7 +758,7 @@ __pthread_rwlock_wrlock_full64 (pthread_rwlock_t *rwlock, clockid_t clockid, } /* We cleaned up and cannot have stolen another waiting writer's futex wake-up, so just return. */ - return ETIMEDOUT; + return err; } /* If we got interrupted (EINTR) or the futex word does not have the expected value (EAGAIN), retry after reloading __readers. */ @@ -829,7 +829,7 @@ __pthread_rwlock_wrlock_full64 (pthread_rwlock_t *rwlock, clockid_t clockid, int err = __futex_abstimed_wait64 (&rwlock->__data.__wrphase_futex, PTHREAD_RWLOCK_FUTEX_USED, clockid, abstime, private); - if (err == ETIMEDOUT) + if (err == ETIMEDOUT || err == EOVERFLOW) { if (rwlock->__data.__flags != PTHREAD_RWLOCK_PREFER_READER_NP) { @@ -861,7 +861,7 @@ __pthread_rwlock_wrlock_full64 (pthread_rwlock_t *rwlock, clockid_t clockid, if ((wf & PTHREAD_RWLOCK_FUTEX_USED) != 0) futex_wake (&rwlock->__data.__writers_futex, 1, private); - return ETIMEDOUT; + return err; } /* TODO Back-off. */ }