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* arch,mips: Convert smp_mb__*()Peter Zijlstra2014-04-181-0/+3
| | | | | | | | | | | | | | | | | | MIPS is interesting and has hardware variants that reorder over ll/sc as well as those that do not. Implement the 2 new barrier functions as per the old barriers. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Link: http://lkml.kernel.org/n/tip-9ph49jbae3hol9v721sbc2g6@git.kernel.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Maciej W. Rozycki" <macro@codesourcery.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Will Deacon <will.deacon@arm.com> Cc: linux-kernel@vger.kernel.org Cc: linux-mips@linux-mips.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* arch: Introduce smp_load_acquire(), smp_store_release()Peter Zijlstra2014-01-121-0/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A number of situations currently require the heavyweight smp_mb(), even though there is no need to order prior stores against later loads. Many architectures have much cheaper ways to handle these situations, but the Linux kernel currently has no portable way to make use of them. This commit therefore supplies smp_load_acquire() and smp_store_release() to remedy this situation. The new smp_load_acquire() primitive orders the specified load against any subsequent reads or writes, while the new smp_store_release() primitive orders the specifed store against any prior reads or writes. These primitives allow array-based circular FIFOs to be implemented without an smp_mb(), and also allow a theoretical hole in rcu_assign_pointer() to be closed at no additional expense on most architectures. In addition, the RCU experience transitioning from explicit smp_read_barrier_depends() and smp_wmb() to rcu_dereference() and rcu_assign_pointer(), respectively resulted in substantial improvements in readability. It therefore seems likely that replacing other explicit barriers with smp_load_acquire() and smp_store_release() will provide similar benefits. It appears that roughly half of the explicit barriers in core kernel code might be so replaced. [Changelog by PaulMck] Reviewed-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Will Deacon <will.deacon@arm.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: Michael Ellerman <michael@ellerman.id.au> Cc: Michael Neuling <mikey@neuling.org> Cc: Russell King <linux@arm.linux.org.uk> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Victor Kaplansky <VICTORK@il.ibm.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Oleg Nesterov <oleg@redhat.com> Link: http://lkml.kernel.org/r/20131213150640.908486364@infradead.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* MIPS: Random whitespace clean-upsMaciej W. Rozycki2013-11-041-3/+3
| | | | | | | | | | Another whitespace clean-up, this removes tabs from between sentences in some comments. Signed-off-by: Maciej W. Rozycki <macro@codesourcery.com> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/6103/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
* MIPS: Whitespace cleanup.Ralf Baechle2013-02-011-5/+5
| | | | | | | | Having received another series of whitespace patches I decided to do this once and for all rather than dealing with this kind of patches trickling in forever. Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
* Disintegrate asm/system.h for MIPSDavid Howells2012-03-281-0/+2
| | | | | | | | Disintegrate asm/system.h for MIPS. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Ralf Baechle <ralf@linux-mips.org> cc: linux-mips@linux-mips.org
* MIPS: Optimize spinlocks.David Daney2010-02-271-0/+6
| | | | | | | | | | | | | | | | | | | | The current locking mechanism uses a ll/sc sequence to release a spinlock. This is slower than a wmb() followed by a store to unlock. The branching forward to .subsection 2 on sc failure slows down the contended case. So we get rid of that part too. Since we are now working on naturally aligned u16 values, we can get rid of a masking operation as the LHU already does the right thing. The ANDI are reversed for better scheduling on multi-issue CPUs On a 12 CPU 750MHz Octeon cn5750 this patch improves ipv4 UDP packet forwarding rates from 3.58*10^6 PPS to 3.99*10^6 PPS, or about 11%. Signed-off-by: David Daney <ddaney@caviumnetworks.com> To: linux-mips@linux-mips.org Patchwork: http://patchwork.linux-mips.org/patch/937/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
* MIPS: Octeon: Use optimized memory barrier primitives.David Daney2010-02-271-12/+31
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In order to achieve correct synchronization semantics, the Octeon port had defined CONFIG_WEAK_REORDERING_BEYOND_LLSC. This resulted in code that looks like: sync ll ... . . . sc ... . . sync The second SYNC was redundant, but harmless. Octeon has a SYNCW instruction that acts as a write-memory-barrier (due to an erratum in some parts two SYNCW are used). It is much faster than SYNC because it imposes ordering on the writes, but doesn't otherwise stall the execution pipeline. On Octeon, SYNC stalls execution until all preceeding writes are committed to the coherent memory system. Using: syncw;syncw ll . . . sc . . Has identical semantics to the first sequence, but is much faster. The SYNCW orders the writes, and the SC will not complete successfully until the write is committed to the coherent memory system. So at the end all preceeding writes have been committed. Since Octeon does not do speculative reads, this functions as a full barrier. The patch removes CONFIG_WEAK_REORDERING_BEYOND_LLSC, and substitutes SYNCW for SYNC in write-memory-barriers. Signed-off-by: David Daney <ddaney@caviumnetworks.com> To: linux-mips@linux-mips.org Patchwork: http://patchwork.linux-mips.org/patch/850/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
* MIPS: New macro smp_mb__before_llsc.David Daney2010-02-271-6/+9
| | | | | | | | | | | | | | | | | Replace some instances of smp_llsc_mb() with a new macro smp_mb__before_llsc(). It is used before ll/sc sequences that are documented as needing write barrier semantics. The default implementation of smp_mb__before_llsc() is just smp_llsc_mb(), so there are no changes in semantics. Also simplify definition of smp_mb(), smp_rmb(), and smp_wmb() to be just barrier() in the non-SMP case. Signed-off-by: David Daney <ddaney@caviumnetworks.com> To: linux-mips@linux-mips.org Patchwork: http://patchwork.linux-mips.org/patch/851/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
* MIPS: Remove unused macros from barrier.hDavid Daney2010-02-271-2/+0
| | | | | | | | | | The smp_llsc_rmb() and smp_llsc_wmb() macros are not used in the tree, remove them. Signed-off-by: David Daney <ddaney@caviumnetworks.com> To: linux-mips@linux-mips.org Patchwork: http://patchwork.linux-mips.org/patch/848/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
* MIPS: Move headfiles to new location below arch/mips/includeRalf Baechle2008-10-111-0/+155
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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