[lkml]   [2019]   [Aug]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-)
On Wed, Aug 21, 2019 at 11:57:03AM -0700, Ira Weiny wrote:

> > Oh, I didn't think we were talking about that. Hanging the close of
> > the datafile fd contingent on some other FD's closure is a recipe for
> > deadlock..
> The discussion between Jan and Dave was concerning what happens when a user
> calls
> fd = open()
> fnctl(...getlease...)
> addr = mmap(fd...)
> ib_reg_mr() <pin>
> munmap(addr...)
> close(fd)

I don't see how blocking close(fd) could work. Write it like this:

fd = open()
uverbs = open(/dev/uverbs)
addr = mmap(fd...)
ib_reg_mr() <pin>

The order FD's are closed during sigkill is not deterministic, so when
all the fputs happen during a kill'd exit we could end up blocking in
close(fd) as close(uverbs) will come after in the close
list. close(uverbs) is the thing that does the dereg_mr and releases
the pin.

We don't need complexity with dup to create problems.


 \ /
  Last update: 2019-08-21 21:48    [W:0.152 / U:7.284 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site