Paul E. McKenney
a792563bd4
rcu: Eliminate read-modify-write ACCESS_ONCE() calls ...
RCU contains code of the following forms:
ACCESS_ONCE(x)++;
ACCESS_ONCE(x) += y;
ACCESS_ONCE(x) -= y;
Now these constructs do operate correctly, but they really result in a
pair of volatile accesses, one to do the load and another to do the store.
This can be confusing, as the casual reader might well assume that (for
example) gcc might generate a memory-to-memory add instruction for each
of these three cases. In fact, gcc will do no such thing. Also, there
is a good chance that the kernel will move to separate load and store
variants of ACCESS_ONCE(), and constructs like the above could easily
confuse both people and scripts attempting to make that sort of change.
Finally, most of RCU's read-modify-write uses of ACCESS_ONCE() really
only need the store to be volatile, so that the read-modify-write form
might be misleading.
This commit therefore changes the above forms in RCU so that each instance
of ACCESS_ONCE() either does a load or a store, but not both. In a few
cases, ACCESS_ONCE() was not critical, for example, for maintaining
statisitics. In these cases, ACCESS_ONCE() has been dispensed with
entirely.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-07-09 09:14:49 -07:00
kernel/printk: use symbolic defines for console loglevels
2014-06-04 16:54:17 -07:00
Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2014-06-12 19:18:49 -07:00
gcov: add support for GCC 4.9
2014-06-10 15:34:46 -07:00
genirq: Improve documentation to match current implementation
2014-05-27 10:16:44 +02:00
Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2014-06-12 18:48:15 -07:00
Merge branch 'pm-sleep'
2014-06-12 13:43:08 +02:00
kernel/printk: use symbolic defines for console loglevels
2014-06-04 16:54:17 -07:00
rcu: Eliminate read-modify-write ACCESS_ONCE() calls
2014-07-09 09:14:49 -07:00
rcu: Reduce overhead of cond_resched() checks for RCU
2014-06-23 11:19:32 -07:00
Merge branch 'akpm' (patchbomb from Andrew) into next
2014-06-04 16:55:13 -07:00
One bug fix that goes back to 3.10. Accessing a non existent buffer
2014-06-12 21:07:25 -07:00
ipc, kernel: clear whitespace
2014-06-06 16:08:14 -07:00
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next
2014-06-12 14:27:40 -07:00
audit: Use struct net not pid_t to remember the network namespce to reply in
2014-03-20 10:10:53 -04:00
inotify: Fix reporting of cookies for inotify events
2014-02-18 11:17:17 +01:00
inotify: Fix reporting of cookies for inotify events
2014-02-18 11:17:17 +01:00
Merge git://git.infradead.org/users/eparis/audit
2014-04-12 12:38:53 -07:00
auditsc: audit_krule mask accesses need bounds checking
2014-06-10 08:44:40 -07:00
kernel/backtracetest.c: replace no level printk by pr_info()
2014-06-04 16:54:14 -07:00
mm: do not allocate page->ptl dynamically, if spinlock_t fits to long
2013-12-20 12:25:45 -08:00
fs,userns: Change inode_capable to capable_wrt_inode_uidgid
2014-06-10 13:57:22 -07:00
Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
2014-06-09 15:03:33 -07:00
cgroup: remove css_parent()
2014-05-16 13:22:48 -04:00
kernel/compat.c: use sizeof() instead of sizeof
2014-06-04 16:54:19 -07:00
asmlinkage: Add explicit __visible to drivers/*, lib/*, kernel/*
2014-05-05 16:07:46 -07:00
More ACPI and power management updates for 3.16-rc1
2014-06-12 13:14:19 -07:00
Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
2014-06-09 15:03:33 -07:00
kernel/exec_domain.c: code clean-up
2014-06-04 16:54:15 -07:00
signals: mv {dis,}allow_signal() from sched.h/exit.c to signal.[ch]
2014-06-06 16:08:11 -07:00
asmlinkage: Make main_extable_sort_needed visible
2014-02-13 18:13:22 -08:00
ptrace: fix fork event messages across pid namespaces
2014-06-06 16:08:11 -07:00
libata, freezer: avoid block device removal while system is frozen
2013-12-19 13:50:32 -05:00
Merge branch 'next' (accumulated 3.16 merge window patches) into master
2014-06-08 11:31:16 -07:00
compat: Get rid of (get|put)_compat_time(val|spec)
2014-02-02 14:09:12 -08:00
kernel/groups.c: remove return value of set_groups
2014-04-03 16:21:05 -07:00
Merge branch 'perf/urgent' into perf/core, to resolve conflict and to prepare for new patches
2014-06-06 07:55:06 +02:00
kernel/hung_task.c: convert simple_strtoul to kstrtouint
2014-06-04 16:54:15 -07:00
perf/x86: Warn to early_printk() in case irq_work is too slow
2014-02-21 21:49:07 +01:00
kernel: use macros from compiler.h instead of __attribute__((...))
2014-04-07 16:36:11 -07:00
locking/rwlocks: Introduce 'qrwlocks' - fair, queued rwlocks
2014-06-06 07:58:28 +02:00
kernel/kexec.c: convert printk to pr_foo()
2014-06-06 16:08:12 -07:00
signals: change wait_for_helper() to use kernel_sigaction()
2014-06-06 16:08:12 -07:00
kprobes: Show blacklist entries via debugfs
2014-04-24 10:26:41 +02:00
kobject: Make support for uevent_helper optional.
2014-04-25 12:00:49 -07:00
kthread: fix return value of kthread_create() upon SIGKILL.
2014-06-04 16:53:51 -07:00
kernel/latencytop.c: convert seq_printf to seq_puts
2014-06-04 16:54:15 -07:00
Merge branch 'x86-asmlinkage-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2014-03-31 14:13:25 -07:00
Most of this is cleaning up various driver sysfs permissions so we can
2014-06-11 16:09:14 -07:00
kprobes, notifier: Use NOKPROBE_SYMBOL macro in notifier
2014-04-24 10:26:39 +02:00
kernel/panic.c: add "crash_kexec_post_notifiers" option for kdump after panic_notifers
2014-06-06 16:08:12 -07:00
param: hand arguments after -- straight to init
2014-04-28 11:48:34 +09:30
pid_namespace: pidns_get() should check task_active_pid_ns() != NULL
2014-04-02 16:20:21 -07:00
kernel/profile.c: use static const char instead of static char
2014-06-06 16:08:13 -07:00
kernel/compat: convert to COMPAT_SYSCALL_DEFINE
2014-03-06 15:35:10 +01:00
kernel/reboot.c: convert simple_strtoul to kstrtoint
2014-06-04 16:54:15 -07:00
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2014-04-12 14:49:50 -07:00
kernel/res_counter.c: replace simple_strtoull by kstrtoull
2014-06-04 16:54:15 -07:00
resources: Clarify sanity check message
2014-05-23 10:47:21 -06:00
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next
2014-06-12 14:27:40 -07:00
signal: Explain local_irq_save() call
2014-07-09 09:14:33 -07:00
smp: print more useful debug info upon receiving IPI on an offline CPU
2014-06-06 16:08:12 -07:00
Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu
2014-05-22 11:36:10 +02:00
kernel/stop_machine.c: kernel-doc warning fix
2014-06-04 16:54:15 -07:00
sched: Consolidate open coded implementations of nice level frobbing into nice_to_rlimit() and rlimit_to_nice()
2014-05-22 11:16:36 +02:00
sys_sgetmask/sys_ssetmask: add CONFIG_SGETMASK_SYSCALL
2014-06-04 16:54:14 -07:00
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next
2014-06-12 14:27:40 -07:00
timer: Prevent overflow in apply_slack
2014-04-30 13:46:17 +02:00
torture: Remove __init from torture_init_begin/end
2014-05-14 09:46:30 -07:00
kernel/tracepoint.c: kernel-doc fixes
2014-06-04 16:54:15 -07:00
smp: Rename __smp_call_function_single() to smp_call_function_single_async()
2014-02-24 14:47:15 -08:00
kernel/user.c: drop unused field 'files' from user_struct
2014-06-04 16:54:16 -07:00
kernel/user_namespace.c: kernel-doc/checkpatch fixes
2014-06-06 16:08:13 -07:00
sysctl: convert use of typedef ctl_table to struct ctl_table
2014-06-06 16:08:16 -07:00
kernel/watchdog.c:touch_softlockup_watchdog(): use raw_cpu_write()
2014-04-18 16:40:08 -07:00
Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
2014-06-09 14:56:49 -07:00
workqueue: rename manager_mutex to attach_mutex
2014-05-20 10:59:32 -04:00
a792563bd4