From: Will Deacon <will.deacon@arm.com>
To: linux-arch@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, Will Deacon <will.deacon@arm.com>,
"Paul E. McKenney" <paulmck@linux.ibm.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Arnd Bergmann <arnd@arndb.de>,
Peter Zijlstra <peterz@infradead.org>,
Andrea Parri <andrea.parri@amarulasolutions.com>,
Palmer Dabbelt <palmer@sifive.com>,
Daniel Lustig <dlustig@nvidia.com>,
David Howells <dhowells@redhat.com>,
Alan Stern <stern@rowland.harvard.edu>,
Linus Torvalds <torvalds@linux-foundation.org>,
"Maciej W. Rozycki" <macro@linux-mips.org>,
Paul Burton <paul.burton@mips.com>,
Ingo Molnar <mingo@kernel.org>,
Yoshinori Sato <ysato@users.sourceforge.jp>,
Rich Felker <dalias@libc.org>, Tony Luck <tony.luck@intel.com>,
Mikulas Patocka <mpatocka@redhat.com>,
Akira Yokosawa <akiyks@gmail.com>,
Luis Chamberlain <mcgrof@kernel.org>,
Nicholas Piggin <npiggin@gmail.com>
Subject: [PATCH v2 02/21] asm-generic/mmiowb: Add generic implementation of mmiowb() tracking
Date: Fri, 5 Apr 2019 14:59:17 +0100 [thread overview]
Message-ID: <20190405135936.7266-3-will.deacon@arm.com> (raw)
In-Reply-To: <20190405135936.7266-1-will.deacon@arm.com>
In preparation for removing all explicit mmiowb() calls from driver
code, implement a tracking system in asm-generic based loosely on the
PowerPC implementation. This allows architectures with a non-empty
mmiowb() definition to have the barrier automatically inserted in
spin_unlock() following a critical section containing an I/O write.
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
include/asm-generic/mmiowb.h | 63 ++++++++++++++++++++++++++++++++++++++
include/asm-generic/mmiowb_types.h | 12 ++++++++
kernel/Kconfig.locks | 7 +++++
kernel/locking/spinlock.c | 7 +++++
4 files changed, 89 insertions(+)
create mode 100644 include/asm-generic/mmiowb.h
create mode 100644 include/asm-generic/mmiowb_types.h
diff --git a/include/asm-generic/mmiowb.h b/include/asm-generic/mmiowb.h
new file mode 100644
index 000000000000..9439ff037b2d
--- /dev/null
+++ b/include/asm-generic/mmiowb.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_GENERIC_MMIOWB_H
+#define __ASM_GENERIC_MMIOWB_H
+
+/*
+ * Generic implementation of mmiowb() tracking for spinlocks.
+ *
+ * If your architecture doesn't ensure that writes to an I/O peripheral
+ * within two spinlocked sections on two different CPUs are seen by the
+ * peripheral in the order corresponding to the lock handover, then you
+ * need to follow these FIVE easy steps:
+ *
+ * 1. Implement mmiowb() (and arch_mmiowb_state() if you're fancy)
+ * in asm/mmiowb.h, then #include this file
+ * 2. Ensure your I/O write accessors call mmiowb_set_pending()
+ * 3. Select ARCH_HAS_MMIOWB
+ * 4. Untangle the resulting mess of header files
+ * 5. Complain to your architects
+ */
+#ifdef CONFIG_MMIOWB
+
+#include <linux/compiler.h>
+#include <asm-generic/mmiowb_types.h>
+
+#ifndef arch_mmiowb_state
+#include <asm/percpu.h>
+#include <asm/smp.h>
+
+DECLARE_PER_CPU(struct mmiowb_state, __mmiowb_state);
+#define __mmiowb_state() this_cpu_ptr(&__mmiowb_state)
+#else
+#define __mmiowb_state() arch_mmiowb_state()
+#endif /* arch_mmiowb_state */
+
+static inline void mmiowb_set_pending(void)
+{
+ struct mmiowb_state *ms = __mmiowb_state();
+ ms->mmiowb_pending = ms->nesting_count;
+}
+
+static inline void mmiowb_spin_lock(void)
+{
+ struct mmiowb_state *ms = __mmiowb_state();
+ ms->nesting_count++;
+}
+
+static inline void mmiowb_spin_unlock(void)
+{
+ struct mmiowb_state *ms = __mmiowb_state();
+
+ if (unlikely(ms->mmiowb_pending)) {
+ ms->mmiowb_pending = 0;
+ mmiowb();
+ }
+
+ ms->nesting_count--;
+}
+#else
+#define mmiowb_set_pending() do { } while (0)
+#define mmiowb_spin_lock() do { } while (0)
+#define mmiowb_spin_unlock() do { } while (0)
+#endif /* CONFIG_MMIOWB */
+#endif /* __ASM_GENERIC_MMIOWB_H */
diff --git a/include/asm-generic/mmiowb_types.h b/include/asm-generic/mmiowb_types.h
new file mode 100644
index 000000000000..8eb0095655e7
--- /dev/null
+++ b/include/asm-generic/mmiowb_types.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_GENERIC_MMIOWB_TYPES_H
+#define __ASM_GENERIC_MMIOWB_TYPES_H
+
+#include <linux/types.h>
+
+struct mmiowb_state {
+ u16 nesting_count;
+ u16 mmiowb_pending;
+};
+
+#endif /* __ASM_GENERIC_MMIOWB_TYPES_H */
diff --git a/kernel/Kconfig.locks b/kernel/Kconfig.locks
index fbba478ae522..6ba2570eddad 100644
--- a/kernel/Kconfig.locks
+++ b/kernel/Kconfig.locks
@@ -251,3 +251,10 @@ config ARCH_USE_QUEUED_RWLOCKS
config QUEUED_RWLOCKS
def_bool y if ARCH_USE_QUEUED_RWLOCKS
depends on SMP
+
+config ARCH_HAS_MMIOWB
+ bool
+
+config MMIOWB
+ def_bool y if ARCH_HAS_MMIOWB
+ depends on SMP
diff --git a/kernel/locking/spinlock.c b/kernel/locking/spinlock.c
index 936f3d14dd6b..0ff08380f531 100644
--- a/kernel/locking/spinlock.c
+++ b/kernel/locking/spinlock.c
@@ -22,6 +22,13 @@
#include <linux/debug_locks.h>
#include <linux/export.h>
+#ifdef CONFIG_MMIOWB
+#ifndef arch_mmiowb_state
+DEFINE_PER_CPU(struct mmiowb_state, __mmiowb_state);
+EXPORT_PER_CPU_SYMBOL(__mmiowb_state);
+#endif
+#endif
+
/*
* If lockdep is enabled then we use the non-preemption spin-ops
* even on CONFIG_PREEMPT, because lockdep assumes that interrupts are
--
2.11.0
next prev parent reply other threads:[~2019-04-05 13:59 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-05 13:59 [PATCH v2 00/21] Remove Mysterious Macro Intended to Obscure Weird Behaviours (mmiowb()) Will Deacon
2019-04-05 13:59 ` [PATCH v2 01/21] docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section Will Deacon
2019-04-10 10:58 ` Ingo Molnar
2019-04-10 12:28 ` Will Deacon
2019-04-11 11:00 ` Ingo Molnar
2019-04-11 22:12 ` Benjamin Herrenschmidt
2019-04-11 22:34 ` Linus Torvalds
2019-04-12 2:07 ` Benjamin Herrenschmidt
2019-04-12 13:17 ` Will Deacon
2019-04-15 4:05 ` Benjamin Herrenschmidt
2019-04-16 9:13 ` Will Deacon
2019-04-05 13:59 ` Will Deacon [this message]
2019-04-05 13:59 ` [PATCH v2 03/21] arch: Use asm-generic header for asm/mmiowb.h Will Deacon
2019-04-05 13:59 ` [PATCH v2 04/21] mmiowb: Hook up mmiowb helpers to spinlocks and generic I/O accessors Will Deacon
2019-04-05 13:59 ` [PATCH v2 05/21] ARM/io: Remove useless definition of mmiowb() Will Deacon
2019-04-05 13:59 ` [PATCH v2 06/21] arm64/io: " Will Deacon
2019-04-05 13:59 ` [PATCH v2 07/21] x86/io: " Will Deacon
2019-04-05 14:14 ` Thomas Gleixner
2019-04-05 13:59 ` [PATCH v2 08/21] nds32/io: " Will Deacon
2019-04-05 13:59 ` [PATCH v2 09/21] m68k/io: " Will Deacon
2019-04-05 13:59 ` [PATCH v2 10/21] sh/mmiowb: Add unconditional mmiowb() to arch_spin_unlock() Will Deacon
2019-04-05 13:59 ` [PATCH v2 11/21] mips/mmiowb: " Will Deacon
2019-04-05 13:59 ` [PATCH v2 12/21] ia64/mmiowb: " Will Deacon
2019-04-05 13:59 ` [PATCH v2 13/21] powerpc/mmiowb: Hook up mmwiob() implementation to asm-generic code Will Deacon
2019-04-05 13:59 ` [PATCH v2 14/21] riscv/mmiowb: " Will Deacon
2019-04-05 13:59 ` [PATCH v2 15/21] Documentation: Kill all references to mmiowb() Will Deacon
2019-04-05 13:59 ` [PATCH v2 16/21] drivers: Remove useless trailing comments from mmiowb() invocations Will Deacon
2019-04-05 13:59 ` [PATCH v2 17/21] drivers: Remove explicit invocations of mmiowb() Will Deacon
2019-04-05 15:50 ` Linus Torvalds
2019-04-09 9:00 ` Nicholas Piggin
2019-04-09 13:46 ` Will Deacon
2019-04-10 0:25 ` Nicholas Piggin
2019-04-05 13:59 ` [PATCH v2 18/21] scsi/qla1280: Remove stale comment about mmiowb() Will Deacon
2019-04-05 13:59 ` [PATCH v2 19/21] i40iw: Redefine i40iw_mmiowb() to do nothing Will Deacon
2019-04-05 13:59 ` [PATCH v2 20/21] net/ethernet/silan/sc92031: Remove stale comment about mmiowb() Will Deacon
2019-04-05 13:59 ` [PATCH v2 21/21] arch: Remove dummy mmiowb() definitions from arch code Will Deacon
2019-04-05 15:55 ` [PATCH v2 00/21] Remove Mysterious Macro Intended to Obscure Weird Behaviours (mmiowb()) Linus Torvalds
2019-04-05 16:09 ` Will Deacon
2019-04-05 16:15 ` Linus Torvalds
2019-04-05 16:30 ` Will Deacon
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