Messages in this thread | | | From | "Wan, Kaike" <> | Subject | RE: [PATCH] IB/sa: replace GFP_KERNEL with GFP_ATOMIC | Date | Tue, 27 Oct 2015 18:56:50 +0000 |
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> -----Original Message----- > From: Jason Gunthorpe [mailto:jgunthorpe@obsidianresearch.com] > Sent: Tuesday, October 27, 2015 2:17 PM > To: Weiny, Ira > Cc: Saurabh Sengar; dledford@redhat.com; Hefty, Sean; > hal.rosenstock@gmail.com; yun.wang@profitbricks.com; Wan, Kaike; linux- > rdma@vger.kernel.org; linux-kernel@vger.kernel.org > Subject: Re: [PATCH] IB/sa: replace GFP_KERNEL with GFP_ATOMIC > > On Tue, Oct 27, 2015 at 02:12:36PM -0400, ira.weiny wrote: > > On Tue, Oct 27, 2015 at 09:17:40PM +0530, Saurabh Sengar wrote: > > > replace GFP_KERNEL with GFP_ATOMIC, as code while holding a spinlock > > > should be atomic GFP_KERNEL may sleep and can cause deadlock, where > > > as GFP_ATOMIC may fail but certainly avoids deadlock > > > > Great catch. Thanks! > > > > However, gfp_t is passed to send_mad and we should pass that down and > use it. > > > spin_lock_irqsave(&ib_nl_request_lock, flags); > > - ret = ib_nl_send_msg(query); > > + ret = ib_nl_send_msg(query, gfp_mask); > > A spin lock is guarenteed held around ib_nl_send_msg, so it's allocations > have to be atomic, can't use gfp_mask here.. > > I do wonder if it is a good idea to call ib_nl_send_msg with a spinlock held > though.. Would be nice to see that go away.
We have to hold the lock to protect against a race condition that a quick response will try to free the request from the ib_nl_request_list before we even put it on the list.
> > Jason
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