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McKenney" , Andy Lutomirski , Dave Watson , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Paul Turner , Andrew Morton , Russell King , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Andrew Hunter , Andi Kleen , Chris Lameter , Ben Maurer , Steven Rostedt , Josh Triplett , Linus Torvalds , Catalin Marinas , Will Deacon , Michael Kerrisk , Alexander Viro Subject: Re: [RFC PATCH for 4.17 02/21] rseq: Introduce restartable sequences system call (v12) Message-ID: <20180328064703.56hsuicmikejg7np@tardis> References: <20180327160542.28457-1-mathieu.desnoyers@efficios.com> <20180327160542.28457-3-mathieu.desnoyers@efficios.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="yzsuj5wf7xcogpl6" Content-Disposition: inline In-Reply-To: <20180327160542.28457-3-mathieu.desnoyers@efficios.com> User-Agent: NeoMutt/20171215 Sender: linux-api-owner@vger.kernel.org X-Mailing-List: linux-api@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: --yzsuj5wf7xcogpl6 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Mar 27, 2018 at 12:05:23PM -0400, Mathieu Desnoyers wrote: [...] > Changes since v11: >=20 > - Replace task struct rseq_preempt, rseq_signal, and rseq_migrate > bool by u32 rseq_event_mask. [...] > @@ -979,6 +980,17 @@ struct task_struct { > unsigned long numa_pages_migrated; > #endif /* CONFIG_NUMA_BALANCING */ > =20 > +#ifdef CONFIG_RSEQ > + struct rseq __user *rseq; > + u32 rseq_len; > + u32 rseq_sig; > + /* > + * RmW on rseq_event_mask must be performed atomically > + * with respect to preemption. > + */ > + unsigned long rseq_event_mask; s/unsigned long/u32 > +#endif > + > struct tlbflush_unmap_batch tlb_ubc; > =20 > struct rcu_head rcu; > @@ -1688,4 +1700,110 @@ extern long sched_getaffinity(pid_t pid, struct c= pumask *mask); > #define TASK_SIZE_OF(tsk) TASK_SIZE > #endif > =20 [...] > + > +static int rseq_ip_fixup(struct pt_regs *regs) > +{ > + unsigned long ip =3D instruction_pointer(regs), start_ip =3D 0, > + post_commit_offset =3D 0, abort_ip =3D 0; > + struct task_struct *t =3D current; > + uint32_t cs_flags =3D 0; > + bool in_rseq_cs =3D false; This seems unnecessary? Because.. > + int ret; > + > + ret =3D rseq_get_rseq_cs(t, &start_ip, &post_commit_offset, &abort_ip, > + &cs_flags); > + if (ret) > + return ret; > + > + /* > + * Handle potentially not being within a critical section. > + * Unsigned comparison will be true when > + * ip >=3D start_ip, and when ip < start_ip + post_commit_offset. > + */ > + if (ip - start_ip < post_commit_offset) > + in_rseq_cs =3D true; > + > + /* > + * If not nested over a rseq critical section, restart is > + * useless. Clear the rseq_cs pointer and return. > + */ > + if (!in_rseq_cs) > + return clear_rseq_cs(t); we can write if (ip - start_ip >=3D post_commit_offset) return clear_rseq_cs(t); Regards, Boqun > + ret =3D rseq_need_restart(t, cs_flags); > + if (ret <=3D 0) > + return ret; > + ret =3D clear_rseq_cs(t); > + if (ret) > + return ret; > + trace_rseq_ip_fixup(ip, start_ip, post_commit_offset, abort_ip); > + instruction_pointer_set(regs, (unsigned long)abort_ip); > + return 0; > +} > + [...] --yzsuj5wf7xcogpl6 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEEj5IosQTPz8XU1wRHSXnow7UH+rgFAlq7OpYACgkQSXnow7UH +rjwhQf+LeKpKOoiYs2E75v4BONhGBr6S9icQvXV25bXj3nlHUJSOW9yHPtN3wjq GwR0eZQkCfKm5ir9BDyRe1L5nKYDWVz7qdj6IDN67yPr6fnAFPw1SNIM8RsOBvn2 d5bLKbPAEJIvv0JWH7VQedq4SlQYfCKPrv0ue45QReE1FsxlDXPt1Aq3El4BUMaw yXEA4xMijOFqk8WOspEjgRkHn/k9jOCKpkVg/dCAu9OZ6Ivqsr4GKvaSpoo9RMfF EqR0/az/GkdJNEh0QlApYNNhBxB+dHd49bMN1K4ql2G7j1St+g6Vdb/3i6KM9PWJ alGOemjl4GXknHu6RE4U9ODYpGUBtQ== =e8tt -----END PGP SIGNATURE----- --yzsuj5wf7xcogpl6--