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6aa7de0591
Please do not apply this to mainline directly, instead please re-run the
coccinelle script shown below and apply its output.
For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't harmful, and changing them results in
churn.
However, for some features, the read/write distinction is critical to
correct operation. To distinguish these cases, separate read/write
accessors must be used. This patch migrates (most) remaining
ACCESS_ONCE() instances to {READ,WRITE}_ONCE(), using the following
coccinelle script:
----
// Convert trivial ACCESS_ONCE() uses to equivalent READ_ONCE() and
// WRITE_ONCE()
// $ make coccicheck COCCI=/home/mark/once.cocci SPFLAGS="--include-headers" MODE=patch
virtual patch
@ depends on patch @
expression E1, E2;
@@
- ACCESS_ONCE(E1) = E2
+ WRITE_ONCE(E1, E2)
@ depends on patch @
expression E;
@@
- ACCESS_ONCE(E)
+ READ_ONCE(E)
----
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: davem@davemloft.net
Cc: linux-arch@vger.kernel.org
Cc: mpe@ellerman.id.au
Cc: shuah@kernel.org
Cc: snitzer@redhat.com
Cc: thor.thayer@linux.intel.com
Cc: tj@kernel.org
Cc: viro@zeniv.linux.org.uk
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
106 lines
2.1 KiB
C
106 lines
2.1 KiB
C
#ifndef _ASM_X86_VGTOD_H
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#define _ASM_X86_VGTOD_H
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#include <linux/compiler.h>
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#include <linux/clocksource.h>
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#ifdef BUILD_VDSO32_64
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typedef u64 gtod_long_t;
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#else
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typedef unsigned long gtod_long_t;
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#endif
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/*
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* vsyscall_gtod_data will be accessed by 32 and 64 bit code at the same time
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* so be carefull by modifying this structure.
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*/
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struct vsyscall_gtod_data {
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unsigned seq;
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int vclock_mode;
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u64 cycle_last;
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u64 mask;
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u32 mult;
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u32 shift;
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/* open coded 'struct timespec' */
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u64 wall_time_snsec;
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gtod_long_t wall_time_sec;
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gtod_long_t monotonic_time_sec;
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u64 monotonic_time_snsec;
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gtod_long_t wall_time_coarse_sec;
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gtod_long_t wall_time_coarse_nsec;
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gtod_long_t monotonic_time_coarse_sec;
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gtod_long_t monotonic_time_coarse_nsec;
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int tz_minuteswest;
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int tz_dsttime;
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};
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extern struct vsyscall_gtod_data vsyscall_gtod_data;
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extern int vclocks_used;
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static inline bool vclock_was_used(int vclock)
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{
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return READ_ONCE(vclocks_used) & (1 << vclock);
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}
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static inline unsigned gtod_read_begin(const struct vsyscall_gtod_data *s)
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{
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unsigned ret;
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repeat:
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ret = READ_ONCE(s->seq);
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if (unlikely(ret & 1)) {
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cpu_relax();
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goto repeat;
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}
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smp_rmb();
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return ret;
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}
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static inline int gtod_read_retry(const struct vsyscall_gtod_data *s,
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unsigned start)
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{
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smp_rmb();
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return unlikely(s->seq != start);
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}
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static inline void gtod_write_begin(struct vsyscall_gtod_data *s)
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{
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++s->seq;
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smp_wmb();
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}
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static inline void gtod_write_end(struct vsyscall_gtod_data *s)
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{
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smp_wmb();
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++s->seq;
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}
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#ifdef CONFIG_X86_64
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#define VGETCPU_CPU_MASK 0xfff
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static inline unsigned int __getcpu(void)
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{
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unsigned int p;
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/*
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* Load per CPU data from GDT. LSL is faster than RDTSCP and
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* works on all CPUs. This is volatile so that it orders
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* correctly wrt barrier() and to keep gcc from cleverly
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* hoisting it out of the calling function.
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*
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* If RDPID is available, use it.
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*/
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alternative_io ("lsl %[p],%[seg]",
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".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */
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X86_FEATURE_RDPID,
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[p] "=a" (p), [seg] "r" (__PER_CPU_SEG));
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return p;
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}
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#endif /* CONFIG_X86_64 */
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#endif /* _ASM_X86_VGTOD_H */
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