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To: Martin KaFai Lau Cc: "David S. Miller" , Daniel Borkmann , Andrii Nakryiko , Tejun Heo , Kumar Kartikeya Dwivedi , Delyan Kratunov , linux-mm , bpf , Kernel Team Content-Type: text/plain; charset="UTF-8" ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661812990; a=rsa-sha256; cv=none; b=MX8sEfbg3/N6lBl/oMB/iHxnUHBb3+hG3lQgJMBXQm4nEqMIm4pvfApJxkN0cPht2ldcg0 oGsxrdMRKtOu01A5CCwybJf97b8kFjbvY0gzBA+KkH8DSD6YzZ56qx5/0lC8SPOx2hWZvo 9NCPsPEDNVYjEvssZaE7s/8oGw75FAs= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="bQ/MW08n"; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf05.hostedemail.com: domain of alexei.starovoitov@gmail.com designates 209.85.218.42 as permitted sender) smtp.mailfrom=alexei.starovoitov@gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661812990; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=nB3G0Zv39kvmVIMxWXDEfEHm0/oHTjvgK70XgH2kXHs=; b=H/ETiOsZTUEVmk1ZcCFwnE1bKCACoKOCDNE7P2fVpDensSp8h3z0Bb0PEifmsnWXVKit6d Ehvld6IDs6HHqp15IZTpUDS7Zl7VDCSliCM5FPGIUeLATGd1TzhltG9GnSf6trM3qavJA3 VEZ9hFg874HlRrYVg4ODyJHY6JdRS6c= X-Rspam-User: X-Rspamd-Queue-Id: 5340E100045 X-Rspamd-Server: rspam12 X-Stat-Signature: u1s6u1zt79e53qag4s8owrjytzbnshe3 Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="bQ/MW08n"; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf05.hostedemail.com: domain of alexei.starovoitov@gmail.com designates 209.85.218.42 as permitted sender) smtp.mailfrom=alexei.starovoitov@gmail.com X-HE-Tag: 1661812990-808573 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Aug 29, 2022 at 3:39 PM Martin KaFai Lau wrote: > > On Thu, Aug 25, 2022 at 07:44:16PM -0700, Alexei Starovoitov wrote: > > +/* Mostly runs from irq_work except __init phase. */ > > +static void alloc_bulk(struct bpf_mem_cache *c, int cnt, int node) > > +{ > > + struct mem_cgroup *memcg = NULL, *old_memcg; > > + unsigned long flags; > > + void *obj; > > + int i; > > + > > + memcg = get_memcg(c); > > + old_memcg = set_active_memcg(memcg); > > + for (i = 0; i < cnt; i++) { > > + obj = __alloc(c, node); > > + if (!obj) > > + break; > > + if (IS_ENABLED(CONFIG_PREEMPT_RT)) > > + /* In RT irq_work runs in per-cpu kthread, so disable > > + * interrupts to avoid preemption and interrupts and > > + * reduce the chance of bpf prog executing on this cpu > > + * when active counter is busy. > > + */ > > + local_irq_save(flags); > > + if (local_inc_return(&c->active) == 1) { > Is it because it is always '== 1' here so that there is > no need to free the obj when it is '!= 1' ? Great catch. It's a bug indeed.