user/sven/linux.git/include/linux/compiler.h, branch v4.0

kernel: make READ_ONCE() valid on const arguments

2015-02-21T18:27:33Z

The use of READ_ONCE() causes lots of warnings witht he pending paravirt spinlock fixes, because those ends up having passing a member to a 'const' structure to READ_ONCE(). There should certainly be nothing wrong with using READ_ONCE() with a const source, but the helper function __read_once_size() would cause warnings because it would drop the 'const' qualifier, but also because the destination would be marked 'const' too due to the use of 'typeof'. Use a union of types in READ_ONCE() to avoid this issue. Also make sure to use parenthesis around the macro arguments to avoid possible operator precedence issues. Tested-by: Ingo Molnar Cc: Christian Borntraeger Signed-off-by: Linus Torvalds

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux

2015-02-14T18:54:28Z

Pull ACCESS_ONCE() rule tightening from Christian Borntraeger: "Tighten rules for ACCESS_ONCE This series tightens the rules for ACCESS_ONCE to only work on scalar types. It also contains the necessary fixups as indicated by build bots of linux-next. Now everything is in place to prevent new non-scalar users of ACCESS_ONCE and we can continue to convert code to READ_ONCE/WRITE_ONCE" * tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux: kernel: Fix sparse warning for ACCESS_ONCE next: sh: Fix compile error kernel: tighten rules for ACCESS ONCE mm/gup: Replace ACCESS_ONCE with READ_ONCE x86/spinlock: Leftover conversion ACCESS_ONCE->READ_ONCE x86/xen/p2m: Replace ACCESS_ONCE with READ_ONCE ppc/hugetlbfs: Replace ACCESS_ONCE with READ_ONCE ppc/kvm: Replace ACCESS_ONCE with READ_ONCE

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

2015-02-12T01:42:32Z

Pull s390 updates from Martin Schwidefsky: - The remaining patches for the z13 machine support: kernel build option for z13, the cache synonym avoidance, SMT support, compare-and-delay for spinloops and the CES5S crypto adapater. - The ftrace support for function tracing with the gcc hotpatch option. This touches common code Makefiles, Steven is ok with the changes. - The hypfs file system gets an extension to access diagnose 0x0c data in user space for performance analysis for Linux running under z/VM. - The iucv hvc console gets wildcard spport for the user id filtering. - The cacheinfo code is converted to use the generic infrastructure. - Cleanup and bug fixes. * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (42 commits) s390/process: free vx save area when releasing tasks s390/hypfs: Eliminate hypfs interval s390/hypfs: Add diagnose 0c support s390/cacheinfo: don't use smp_processor_id() in preemptible context s390/zcrypt: fixed domain scanning problem (again) s390/smp: increase maximum value of NR_CPUS to 512 s390/jump label: use different nop instruction s390/jump label: add sanity checks s390/mm: correct missing space when reporting user process faults s390/dasd: cleanup profiling s390/dasd: add locking for global_profile access s390/ftrace: hotpatch support for function tracing ftrace: let notrace function attribute disable hotpatching if necessary ftrace: allow architectures to specify ftrace compile options s390: reintroduce diag 44 calls for cpu_relax() s390/zcrypt: Add support for new crypto express (CEX5S) adapter. s390/zcrypt: Number of supported ap domains is not retrievable. s390/spinlock: add compare-and-delay to lock wait loops s390/tape: remove redundant if statement s390/hvc_iucv: add simple wildcard matches to the iucv allow filter ...

ftrace: let notrace function attribute disable hotpatching if necessary

2015-01-29T08:19:23Z

gcc supports an s390 specific function attribute called "hotpatch". It can be used to specify the number of halfwords that shall be added before and after a function and which shall be filled with nops for runtime patching. s390 will use the hotpatch attribute for function tracing, therefore make sure that the notrace function attribute either disables the mcount call or in case of hotpatch nop generation. Acked-by: Steven Rostedt Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

2015-01-21T05:12:21Z

Pull RCU updates from Paul E. McKenney: - Documentation updates. - Miscellaneous fixes. - Preemptible-RCU fixes, including fixing an old bug in the interaction of RCU priority boosting and CPU hotplug. - SRCU updates. - RCU CPU stall-warning updates. - RCU torture-test updates. Signed-off-by: Ingo Molnar

kernel: Fix sparse warning for ACCESS_ONCE

2015-01-19T13:15:00Z

Commit 927609d622a3 ("kernel: tighten rules for ACCESS ONCE") results in sparse warnings like "Using plain integer as NULL pointer" - Let's add a type cast to the dummy assignment. To avoid warnings lik "sparse: warning: cast to restricted __hc32" we also use __force on that cast. Fixes: 927609d622a3 ("kernel: tighten rules for ACCESS ONCE") Signed-off-by: Christian Borntraeger

kernel: tighten rules for ACCESS ONCE

2015-01-19T13:14:21Z

Now that all non-scalar users of ACCESS_ONCE have been converted to READ_ONCE or ASSIGN once, lets tighten ACCESS_ONCE to only work on scalar types. This variant was proposed by Alexei Starovoitov. Signed-off-by: Christian Borntraeger Reviewed-by: Paul E. McKenney

kernel: Change ASSIGN_ONCE(val, x) to WRITE_ONCE(x, val)

2015-01-13T19:39:09Z

Feedback has shown that WRITE_ONCE(x, val) is easier to use than ASSIGN_ONCE(val,x). There are no in-tree users yet, so lets change it for 3.19. Signed-off-by: Christian Borntraeger Acked-by: Peter Zijlstra Acked-by: Davidlohr Bueso Acked-by: Paul E. McKenney

compiler: Allow 1- and 2-byte smp_load_acquire() and smp_store_release()

2015-01-06T19:01:09Z

CPUs without single-byte and double-byte loads and stores place some "interesting" requirements on concurrent code. For example (adapted from Peter Hurley's test code), suppose we have the following structure: struct foo { spinlock_t lock1; spinlock_t lock2; char a; /* Protected by lock1. */ char b; /* Protected by lock2. */ }; struct foo *foop; Of course, it is common (and good) practice to place data protected by different locks in separate cache lines. However, if the locks are rarely acquired (for example, only in rare error cases), and there are a great many instances of the data structure, then memory footprint can trump false-sharing concerns, so that it can be better to place them in the same cache cache line as above. But if the CPU does not support single-byte loads and stores, a store to foop->a will do a non-atomic read-modify-write operation on foop->b, which will come as a nasty surprise to someone holding foop->lock2. So we now require CPUs to support single-byte and double-byte loads and stores. Therefore, this commit adjusts the definition of __native_word() to allow these sizes to be used by smp_load_acquire() and smp_store_release(). Signed-off-by: Paul E. McKenney Cc: Peter Zijlstra

kernel: Provide READ_ONCE and ASSIGN_ONCE

2014-12-18T08:54:36Z

ACCESS_ONCE does not work reliably on non-scalar types. For example gcc 4.6 and 4.7 might remove the volatile tag for such accesses during the SRA (scalar replacement of aggregates) step https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145) Let's provide READ_ONCE/ASSIGN_ONCE that will do all accesses via scalar types as suggested by Linus Torvalds. Accesses larger than the machines word size cannot be guaranteed to be atomic. These macros will use memcpy and emit a build warning. Signed-off-by: Christian Borntraeger