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[209.85.220.65]) by mx.google.com with SMTPS id m3sor9000133qki.54.2019.06.18.06.40.39 for (Google Transport Security); Tue, 18 Jun 2019 06:40:39 -0700 (PDT) Received-SPF: pass (google.com: domain of joelaf@google.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=QooPXmn9; spf=pass (google.com: domain of joelaf@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=joelaf@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=ZI5wHdiFgtuzsQeLY+E22h5PJMnK0tB2yGyNBxZfSqI=; b=QooPXmn9aHah5NAlG4PfOfya5KeBRPEo/cvd64QxdYAB2AkodS68j+GjfPi84y88a8 DuB0moLc60pdiekoXOCOsAxtghv/tzyS0Zmk+0MTZYsCOMvXwdivw9V7wUKoLv6q4Axg 5s6bDCqaOyBCLr0QLrvUxRJ36c87CczbZqr7489CDIbk5w73LorhbzV6/p+ILdWmi3EO QBo9JXpFB/Ht4FqcBxvorRa1+QvlOIMjcuwGXXSs2RW1sMA4cGX4JDaIo7BcsPKhNArX 7PXLzk7LUCtr49cSwuHKA+oMLhBIasoWAkwIyRCAeENSKRYKtox2kQoezDn3ZK5Mwul7 Q7yw== X-Google-Smtp-Source: APXvYqydIfBeJNwoqU7hLKDek16QVNj311nTvALhVsaWemQl/rKnPG8IXP59Ccqe5Lnh87RqflvTK1whFaMyh7g4f+8= X-Received: by 2002:a37:696:: with SMTP id 144mr91098200qkg.250.1560865239273; Tue, 18 Jun 2019 06:40:39 -0700 (PDT) MIME-Version: 1.0 References: <20190618092650.2943749-1-arnd@arndb.de> In-Reply-To: <20190618092650.2943749-1-arnd@arndb.de> From: Joel Fernandes Date: Tue, 18 Jun 2019 09:40:28 -0400 Message-ID: Subject: Re: [PATCH] mm/vmalloc: avoid bogus -Wmaybe-uninitialized warning To: Arnd Bergmann Cc: Roman Penyaev , Uladzislau Rezki , Andrew Morton , "open list:MEMORY MANAGEMENT" , Roman Gushchin , Michal Hocko , Matthew Wilcox , Thomas Garnier , Oleksiy Avramchenko , Steven Rostedt , Thomas Gleixner , Ingo Molnar , Tejun Heo , Linus Torvalds , Rick Edgecombe , Andrey Ryabinin , Mike Rapoport , LKML 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: On Tue, Jun 18, 2019 at 5:27 AM Arnd Bergmann wrote: > > gcc gets confused in pcpu_get_vm_areas() because there are too many > branches that affect whether 'lva' was initialized before it gets > used: > > mm/vmalloc.c: In function 'pcpu_get_vm_areas': > mm/vmalloc.c:991:4: error: 'lva' may be used uninitialized in this function [-Werror=maybe-uninitialized] > insert_vmap_area_augment(lva, &va->rb_node, > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > &free_vmap_area_root, &free_vmap_area_list); > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > mm/vmalloc.c:916:20: note: 'lva' was declared here > struct vmap_area *lva; > ^~~ > > Add an intialization to NULL, and check whether this has changed > before the first use. > > Fixes: 68ad4a330433 ("mm/vmalloc.c: keep track of free blocks for vmap allocation") > Signed-off-by: Arnd Bergmann > --- > mm/vmalloc.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index a9213fc3802d..42a6f795c3ee 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -913,7 +913,12 @@ adjust_va_to_fit_type(struct vmap_area *va, > unsigned long nva_start_addr, unsigned long size, > enum fit_type type) > { > - struct vmap_area *lva; > + /* > + * GCC cannot always keep track of whether this variable > + * was initialized across many branches, therefore set > + * it NULL here to avoid a warning. > + */ > + struct vmap_area *lva = NULL; Fair enough, but is this 5-line comment really needed here? - Joel