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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 6 Dec 2019 10:59:06 -0800
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Subject: Re: [PATCH 0/2] pipe: Fixes [ver #2]
To:     David Sterba <dsterba@suse.cz>,
        David Howells <dhowells@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Eric Biggers <ebiggers@kernel.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Hmm. I think I just saw this same bug with a plain kernel compile.

My "make -j32" suddenly came to a crawl, and seems to be entirely
single-threaded.

And that's almost certainly because the way 'make' handles load
distribution is with a network of pipes that has a token passed to the
sub-makes.

So there's most definitely something wrong with the new pipe rework.
Well, I can't _guarantee_ the pipes are the cause of this, but it does
smell like it.

              Linus