tree eaabf46fb352ed526a918ee7fb3ab17be4a4cc61
parent b8c8a9590e4fde82f8c3ee06a521763e6f21e9c8
author Jim Wilson <jimw@sifive.com> 1539726179 -0700
committer Palmer Dabbelt <palmer@sifive.com> 1540255088 -0700
gpgsig -----BEGIN PGP SIGNATURE-----
 
 iQJHBAABCAAxFiEEAM520YNJYN/OiG3470yhUCzLq0EFAlvObXATHHBhbG1lckBk
 YWJiZWx0LmNvbQAKCRDvTKFQLMurQcTsD/oDMLOheCIbRxkWAX+TedjdYiFvtDYz
 dv7gjyaUb1S/KjHgjjjB2glr9B0xdFva/ytVpm63fFT14LWuQuQeCx9OuA/Xq+d3
 +6nV9391nyiA/1kZGFs0f7EeF+zED8Fxp+T47K5Yr3WORHmvjcuNe/sH+lrvA7qL
 y07qeZFebsj7B9ehNJTm402pq9tan3tZr3gLS6beoBjS789kIK2nLH8vb0Widuy6
 o1GlzaU+SBfNVLImddmO7aHO1DGz+4GmJW0HhbvWRtPWtDgHpncTxxCRwQIZZCk+
 IDsd5XopizJNsr3x0zTKnfUw3jN/Wz5YAcWrc4ALWdHLskyhuM+rcMJGR2VHUJJF
 KoG/yhhkqwtD4Zxz724Kz8EvPMOz0QdFHB7fzHWie+Wlh3dhJJOLF1DnezkEhrBg
 OUeswh6d6P14PWcR+IAMMTx6mpQjiO9HnG3fuH4des4cUyRr9plifGPM74zriW/J
 MnIamVHVO8mJVf865G1uEeJHx5Ce+1lgTFk5RqBSUGqMutPzYC7LQh70NHPbQ2Ny
 j3AWNEsUUChq+m1oUQseGrOCREUR3QT4oXd5xzq2jCQ4/cXXErrEobUb3hMqnRKz
 od7mxepDUL9sM2zuEGYWUOp40JUed3ND5Elo0I0EqAUqzgwvQeVDTbqMKNJPA97m
 YTmqnPdwObauCw==
 =b7G6
 -----END PGP SIGNATURE-----

RISC-V: Add futex support.

Here is an attempt to add the missing futex support.  I started with the MIPS
version of futex.h and modified it until I got it working.  I tested it on
a HiFive Unleashed running Fedora Core 29 using the fc29 4.15 version of the
kernel.  This was tested against the glibc testsuite, where it fixes 14 nptl
related testsuite failures.  That unfortunately only tests the cmpxchg support,
so I also used the testcase at the end of

    https://lwn.net/Articles/148830/

which tests the atomic_op functionality, except that it doesn't verify that
the operations are atomic, which they obviously are.  This testcase runs
successfully with the patch and fails without it.

I'm not a kernel expert, so there could be details I got wrong here.  I wasn't
sure about the memory model support, so I used aqrl which seemed safest, and
didn't add fences which seemed unnecessary.  I'm not sure about the copyright
statements, I left in Ralf Baechle's line because I started with his code.
Checkpatch reports some style problems, but it is the same style as the MIPS
futex.h, and the uses of ENOSYS appear correct even though it complains about
them.  I don't know if any of that matters.

This patch was tested on qemu with the glibc nptl/tst-cond-except
testcase, and the wake_op testcase from above.

Signed-off-by: Jim Wilson <jimw@sifive.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>