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 2C304C38A29 for ; Wed, 15 Apr 2020 00:44:19 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CE06220737 for ; Wed, 15 Apr 2020 00:44:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="j2mj8y6m" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CE06220737 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EB3498E000D; Tue, 14 Apr 2020 20:44:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E8B1C8E000B; Tue, 14 Apr 2020 20:44:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DA1108E000D; Tue, 14 Apr 2020 20:44:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0131.hostedemail.com [216.40.44.131]) by kanga.kvack.org (Postfix) with ESMTP id C2A248E000B for ; Tue, 14 Apr 2020 20:44:14 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 87010181AEF1E for ; Wed, 15 Apr 2020 00:44:14 +0000 (UTC) X-FDA: 76708242828.10.bean78_4219864492c0e X-HE-Tag: bean78_4219864492c0e X-Filterd-Recvd-Size: 6107 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) by imf47.hostedemail.com (Postfix) with ESMTP for ; Wed, 15 Apr 2020 00:44:14 +0000 (UTC) Received: by mail-pg1-f201.google.com with SMTP id x16so1374218pgi.0 for ; Tue, 14 Apr 2020 17:44:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=W/v3+M/LWfOzs3/FZNGrbIM1gxpJLCv1N1Vd1+pldaA=; b=j2mj8y6mS6PkrzUFtRlLk6MSDpFJnBFHJMwSaTTAd3UOVKRe9MVLx0m54Z1gRUuyl0 ixVszlruHE07ytSByL8p5M6+AvxWxNI14AdIkkHGqccSniAyFLzqwnPfP3QEhIbrlf0Y 4kkTm5CeFhbBGoO2TRwi4Te5P0AQAxPg8EybmZsg+8D7AikDPHY9KDtORGy+4EI4PKkG RLGbepFP9xj0tTA4cGy2vpV8MqIIX6ezqX0p5paF/6e/0PTh0LxmAPCAxr3Ds3TUP+ab oez2T8VF8eln54Yog2Ec6E9nE5rGjrP0e4S4NDMXDrRmHtQOB0YJRSF3MSe6IwqzFgPU zIGw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=W/v3+M/LWfOzs3/FZNGrbIM1gxpJLCv1N1Vd1+pldaA=; b=QkqhB+2C4AO0TuXkAGRc0uAS+NkeTyX7stGpdT0ch2WINylnujtz/pV/z0pZ3OFiDx fOmc2XfyH4AkvUHZvZo05SBJDe8FeGoTM5w0sIuJcSH34YWkP65aYjh4i4Gp4fg73FRE cVTrLRMnOJaTeaPzxfwghdE/Ob5ntbmGkGk6ZxbTNkeC+FEFI5MSM6JIH/dKL90Bv9Yh pfO4ESRWfnonwwaQLCmQ7KfIkVqjb3SH0CP31sQOYaWkRJvjvhhOzEP5dRZp6DEGhNZq VkOepgEzYsDJsfJwk9YrmpfKSeFUgq2ygeW+jYoLoyMS7+d385RARp+TPZOo9nKkow1l SOwQ== X-Gm-Message-State: AGi0PuYMlm5AQQBldjAfXeDcaigTCktya+xAe9Dq3G78cVACem9E2NRW zsg2+rQH1q56URJv+AGL5Vm7EoGqodk= X-Google-Smtp-Source: APiQypJAv6NRWZVPw+zLkQyYQ4PLNAZh/M8C8AdziwMW8P44l6wCvQkIrjiBt5eRFbVPbPRbtYA7nKmqq8k= X-Received: by 2002:a17:90a:bb8d:: with SMTP id v13mr3232376pjr.150.1586911453265; Tue, 14 Apr 2020 17:44:13 -0700 (PDT) Date: Tue, 14 Apr 2020 17:43:50 -0700 In-Reply-To: <20200415004353.130248-1-walken@google.com> Message-Id: <20200415004353.130248-8-walken@google.com> Mime-Version: 1.0 References: <20200415004353.130248-1-walken@google.com> X-Mailer: git-send-email 2.26.0.110.g2183baf09c-goog Subject: [PATCH v4 07/10] mmap locking API: add mmap_read_trylock_non_owner() From: Michel Lespinasse To: Andrew Morton , linux-mm Cc: LKML , Peter Zijlstra , Laurent Dufour , Vlastimil Babka , Matthew Wilcox , Liam Howlett , Jerome Glisse , Davidlohr Bueso , David Rientjes , Hugh Dickins , Ying Han , Jason Gunthorpe , Daniel Jordan , Michel Lespinasse Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Add a couple APIs used by kernel/bpf/stackmap.c only: - mmap_read_trylock_non_owner() - mmap_read_unlock_non_owner() (may be called from a work queue). It's still not ideal that bpf/stackmap subverts the lock ownership in this way. Thanks to Peter Zijlstra for suggesting this API as the least-ugly way of addressing this in the short term. Signed-off-by: Michel Lespinasse --- include/linux/mmap_lock.h | 14 ++++++++++++++ kernel/bpf/stackmap.c | 17 +++++------------ 2 files changed, 19 insertions(+), 12 deletions(-) diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h index 9d34b0690403..1050257361aa 100644 --- a/include/linux/mmap_lock.h +++ b/include/linux/mmap_lock.h @@ -56,4 +56,18 @@ static inline void mmap_read_unlock(struct mm_struct *mm) up_read(&mm->mmap_sem); } +static inline bool mmap_read_trylock_non_owner(struct mm_struct *mm) +{ + if (down_read_trylock(&mm->mmap_sem)) { + rwsem_release(&mm->mmap_sem.dep_map, _RET_IP_); + return true; + } + return false; +} + +static inline void mmap_read_unlock_non_owner(struct mm_struct *mm) +{ + up_read_non_owner(&mm->mmap_sem); +} + #endif /* _LINUX_MMAP_LOCK_H */ diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 11d41f0c7005..998968659892 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -33,7 +33,7 @@ struct bpf_stack_map { /* irq_work to run up_read() for build_id lookup in nmi context */ struct stack_map_irq_work { struct irq_work irq_work; - struct rw_semaphore *sem; + struct mm_struct *mm; }; static void do_up_read(struct irq_work *entry) @@ -44,8 +44,7 @@ static void do_up_read(struct irq_work *entry) return; work = container_of(entry, struct stack_map_irq_work, irq_work); - up_read_non_owner(work->sem); - work->sem = NULL; + mmap_read_unlock_non_owner(work->mm); } static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work); @@ -317,7 +316,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, * with build_id. */ if (!user || !current || !current->mm || irq_work_busy || - mmap_read_trylock(current->mm) == 0) { + !mmap_read_trylock_non_owner(current->mm)) { /* cannot access current->mm, fall back to ips */ for (i = 0; i < trace_nr; i++) { id_offs[i].status = BPF_STACK_BUILD_ID_IP; @@ -342,16 +341,10 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, } if (!work) { - mmap_read_unlock(current->mm); + mmap_read_unlock_non_owner(current->mm); } else { - work->sem = ¤t->mm->mmap_sem; + work->mm = current->mm; irq_work_queue(&work->irq_work); - /* - * The irq_work will release the mmap_sem with - * up_read_non_owner(). The rwsem_release() is called - * here to release the lock from lockdep's perspective. - */ - rwsem_release(¤t->mm->mmap_sem.dep_map, _RET_IP_); } } -- 2.26.0.110.g2183baf09c-goog