From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Shi, Yang" Subject: Re: [PATCH] bpf: convert hashtab lock to raw lock Date: Mon, 02 Nov 2015 09:09:03 -0800 Message-ID: <563798AF.7000505@linaro.org> References: <1446243386-26582-1-git-send-email-yang.shi@linaro.org> <20151031000356.GA28070@Alexeis-MacBook-Pro.local> <20151031094736.494427d7@grimm.local.home> <20151101225620.GA28272@Alexeis-MacBook-Pro.local> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: ast@kernel.org, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, netdev@vger.kernel.org, linaro-kernel@lists.linaro.org To: Thomas Gleixner , Alexei Starovoitov , Steven Rostedt Return-path: In-Reply-To: Sender: netdev-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org On 11/2/2015 12:59 AM, Thomas Gleixner wrote: > On Sun, 1 Nov 2015, Alexei Starovoitov wrote: >> On Sat, Oct 31, 2015 at 09:47:36AM -0400, Steven Rostedt wrote: >>> On Fri, 30 Oct 2015 17:03:58 -0700 >>> Alexei Starovoitov wrote: >>> >>>> On Fri, Oct 30, 2015 at 03:16:26PM -0700, Yang Shi wrote: >>>>> When running bpf samples on rt kernel, it reports the below warning: >>>>> >>>>> BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:917 >>>>> in_atomic(): 1, irqs_disabled(): 128, pid: 477, name: ping >>>>> Preemption disabled at:[] kprobe_perf_func+0x30/0x228 >>>> ... >>>>> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c >>>>> index 83c209d..972b76b 100644 >>>>> --- a/kernel/bpf/hashtab.c >>>>> +++ b/kernel/bpf/hashtab.c >>>>> @@ -17,7 +17,7 @@ >>>>> struct bpf_htab { >>>>> struct bpf_map map; >>>>> struct hlist_head *buckets; >>>>> - spinlock_t lock; >>>>> + raw_spinlock_t lock; >>>> >>>> How do we address such things in general? >>>> I bet there are tons of places around the kernel that >>>> call spin_lock from atomic. >>>> I'd hate to lose the benefits of lockdep of non-raw spin_lock >>>> just to make rt happy. >>> >>> You wont lose any benefits of lockdep. Lockdep still checks >>> raw_spin_lock(). The only difference between raw_spin_lock and >>> spin_lock is that in -rt spin_lock turns into an rt_mutex() and >>> raw_spin_lock stays a spin lock. >> >> I see. The patch makes sense then. >> Would be good to document this peculiarity of spin_lock. > > I'm working on a document. Thanks Steven and Thomas for your elaboration and comment. Yang > > Thanks, > > tglx >