From d89e588ca4081615216cc25f2489b0281ac0bfe9 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 5 Sep 2016 11:37:53 +0200 Subject: locking: Introduce smp_mb__after_spinlock() Since its inception, our understanding of ACQUIRE, esp. as applied to spinlocks, has changed somewhat. Also, I wonder if, with a simple change, we cannot make it provide more. The problem with the comment is that the STORE done by spin_lock isn't itself ordered by the ACQUIRE, and therefore a later LOAD can pass over it and cross with any prior STORE, rendering the default WMB insufficient (pointed out by Alan). Now, this is only really a problem on PowerPC and ARM64, both of which already defined smp_mb__before_spinlock() as a smp_mb(). At the same time, we can get a much stronger construct if we place that same barrier _inside_ the spin_lock(). In that case we upgrade the RCpc spinlock to an RCsc. That would make all schedule() calls fully transitive against one another. Signed-off-by: Peter Zijlstra (Intel) Acked-by: Will Deacon Cc: Alan Stern Cc: Benjamin Herrenschmidt Cc: Linus Torvalds Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Oleg Nesterov Cc: Paul McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar --- arch/powerpc/include/asm/spinlock.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch/powerpc/include') diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h index 8c1b913de6d7..c1b1ec94b06c 100644 --- a/arch/powerpc/include/asm/spinlock.h +++ b/arch/powerpc/include/asm/spinlock.h @@ -342,5 +342,8 @@ static inline void arch_write_unlock(arch_rwlock_t *rw) #define arch_read_relax(lock) __rw_yield(lock) #define arch_write_relax(lock) __rw_yield(lock) +/* See include/linux/spinlock.h */ +#define smp_mb__after_spinlock() smp_mb() + #endif /* __KERNEL__ */ #endif /* __ASM_SPINLOCK_H */ -- cgit v1.2.3 From a9668cd6ee288c4838bc668880ac085be551cac2 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 7 Jun 2017 17:51:27 +0200 Subject: locking: Remove smp_mb__before_spinlock() Now that there are no users of smp_mb__before_spinlock() left, remove it entirely. Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar --- arch/powerpc/include/asm/barrier.h | 7 ------- 1 file changed, 7 deletions(-) (limited to 'arch/powerpc/include') diff --git a/arch/powerpc/include/asm/barrier.h b/arch/powerpc/include/asm/barrier.h index 25d42bd3f114..9c601adfc500 100644 --- a/arch/powerpc/include/asm/barrier.h +++ b/arch/powerpc/include/asm/barrier.h @@ -74,13 +74,6 @@ do { \ ___p1; \ }) -/* - * This must resolve to hwsync on SMP for the context switch path. - * See _switch, and core scheduler context switch memory ordering - * comments. - */ -#define smp_mb__before_spinlock() smp_mb() - #include #endif /* _ASM_POWERPC_BARRIER_H */ -- cgit v1.2.3 From 30d6e0a4190d37740e9447e4e4815f06992dd8c3 Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Thu, 24 Aug 2017 09:31:05 +0200 Subject: futex: Remove duplicated code and fix undefined behaviour There is code duplicated over all architecture's headers for futex_atomic_op_inuser. Namely op decoding, access_ok check for uaddr, and comparison of the result. Remove this duplication and leave up to the arches only the needed assembly which is now in arch_futex_atomic_op_inuser. This effectively distributes the Will Deacon's arm64 fix for undefined behaviour reported by UBSAN to all architectures. The fix was done in commit 5f16a046f8e1 (arm64: futex: Fix undefined behaviour with FUTEX_OP_OPARG_SHIFT usage). Look there for an example dump. And as suggested by Thomas, check for negative oparg too, because it was also reported to cause undefined behaviour report. Note that s390 removed access_ok check in d12a29703 ("s390/uaccess: remove pointless access_ok() checks") as access_ok there returns true. We introduce it back to the helper for the sake of simplicity (it gets optimized away anyway). Signed-off-by: Jiri Slaby Signed-off-by: Thomas Gleixner Acked-by: Russell King Acked-by: Michael Ellerman (powerpc) Acked-by: Heiko Carstens [s390] Acked-by: Chris Metcalf [for tile] Reviewed-by: Darren Hart (VMware) Reviewed-by: Will Deacon [core/arm64] Cc: linux-mips@linux-mips.org Cc: Rich Felker Cc: linux-ia64@vger.kernel.org Cc: linux-sh@vger.kernel.org Cc: peterz@infradead.org Cc: Benjamin Herrenschmidt Cc: Max Filippov Cc: Paul Mackerras Cc: sparclinux@vger.kernel.org Cc: Jonas Bonn Cc: linux-s390@vger.kernel.org Cc: linux-arch@vger.kernel.org Cc: Yoshinori Sato Cc: linux-hexagon@vger.kernel.org Cc: Helge Deller Cc: "James E.J. Bottomley" Cc: Catalin Marinas Cc: Matt Turner Cc: linux-snps-arc@lists.infradead.org Cc: Fenghua Yu Cc: Arnd Bergmann Cc: linux-xtensa@linux-xtensa.org Cc: Stefan Kristiansson Cc: openrisc@lists.librecores.org Cc: Ivan Kokshaysky Cc: Stafford Horne Cc: linux-arm-kernel@lists.infradead.org Cc: Richard Henderson Cc: Chris Zankel Cc: Michal Simek Cc: Tony Luck Cc: linux-parisc@vger.kernel.org Cc: Vineet Gupta Cc: Ralf Baechle Cc: Richard Kuo Cc: linux-alpha@vger.kernel.org Cc: Martin Schwidefsky Cc: linuxppc-dev@lists.ozlabs.org Cc: "David S. Miller" Link: http://lkml.kernel.org/r/20170824073105.3901-1-jslaby@suse.cz --- arch/powerpc/include/asm/futex.h | 26 +++++--------------------- 1 file changed, 5 insertions(+), 21 deletions(-) (limited to 'arch/powerpc/include') diff --git a/arch/powerpc/include/asm/futex.h b/arch/powerpc/include/asm/futex.h index eaada6c92344..719ed9b61ea7 100644 --- a/arch/powerpc/include/asm/futex.h +++ b/arch/powerpc/include/asm/futex.h @@ -29,18 +29,10 @@ : "b" (uaddr), "i" (-EFAULT), "r" (oparg) \ : "cr0", "memory") -static inline int futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr) +static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval, + u32 __user *uaddr) { - int op = (encoded_op >> 28) & 7; - int cmp = (encoded_op >> 24) & 15; - int oparg = (encoded_op << 8) >> 20; - int cmparg = (encoded_op << 20) >> 20; int oldval = 0, ret; - if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28)) - oparg = 1 << oparg; - - if (! access_ok (VERIFY_WRITE, uaddr, sizeof(u32))) - return -EFAULT; pagefault_disable(); @@ -66,17 +58,9 @@ static inline int futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr) pagefault_enable(); - if (!ret) { - switch (cmp) { - case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break; - case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break; - case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break; - case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break; - case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break; - case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break; - default: ret = -ENOSYS; - } - } + if (!ret) + *oval = oldval; + return ret; } -- cgit v1.2.3