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author | Linus Torvalds <torvalds@linux-foundation.org> | 2014-08-05 17:46:42 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-08-05 17:46:42 -0700 |
commit | e7fda6c4c3c1a7d6996dd75fd84670fa0b5d448f (patch) | |
tree | daa51c16462c318b890acf7f01fba5827275dd74 /include/linux/seqlock.h | |
parent | 08d69a25714429850cf9ef71f22d8cdc9189d93f (diff) | |
parent | 953dec21aed4038464fec02f96a2f1b8701a5bce (diff) | |
download | lwn-e7fda6c4c3c1a7d6996dd75fd84670fa0b5d448f.tar.gz lwn-e7fda6c4c3c1a7d6996dd75fd84670fa0b5d448f.zip |
Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer and time updates from Thomas Gleixner:
"A rather large update of timers, timekeeping & co
- Core timekeeping code is year-2038 safe now for 32bit machines.
Now we just need to fix all in kernel users and the gazillion of
user space interfaces which rely on timespec/timeval :)
- Better cache layout for the timekeeping internal data structures.
- Proper nanosecond based interfaces for in kernel users.
- Tree wide cleanup of code which wants nanoseconds but does hoops
and loops to convert back and forth from timespecs. Some of it
definitely belongs into the ugly code museum.
- Consolidation of the timekeeping interface zoo.
- A fast NMI safe accessor to clock monotonic for tracing. This is a
long standing request to support correlated user/kernel space
traces. With proper NTP frequency correction it's also suitable
for correlation of traces accross separate machines.
- Checkpoint/restart support for timerfd.
- A few NOHZ[_FULL] improvements in the [hr]timer code.
- Code move from kernel to kernel/time of all time* related code.
- New clocksource/event drivers from the ARM universe. I'm really
impressed that despite an architected timer in the newer chips SoC
manufacturers insist on inventing new and differently broken SoC
specific timers.
[ Ed. "Impressed"? I don't think that word means what you think it means ]
- Another round of code move from arch to drivers. Looks like most
of the legacy mess in ARM regarding timers is sorted out except for
a few obnoxious strongholds.
- The usual updates and fixlets all over the place"
* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (114 commits)
timekeeping: Fixup typo in update_vsyscall_old definition
clocksource: document some basic timekeeping concepts
timekeeping: Use cached ntp_tick_length when accumulating error
timekeeping: Rework frequency adjustments to work better w/ nohz
timekeeping: Minor fixup for timespec64->timespec assignment
ftrace: Provide trace clocks monotonic
timekeeping: Provide fast and NMI safe access to CLOCK_MONOTONIC
seqcount: Add raw_write_seqcount_latch()
seqcount: Provide raw_read_seqcount()
timekeeping: Use tk_read_base as argument for timekeeping_get_ns()
timekeeping: Create struct tk_read_base and use it in struct timekeeper
timekeeping: Restructure the timekeeper some more
clocksource: Get rid of cycle_last
clocksource: Move cycle_last validation to core code
clocksource: Make delta calculation a function
wireless: ath9k: Get rid of timespec conversions
drm: vmwgfx: Use nsec based interfaces
drm: i915: Use nsec based interfaces
timekeeping: Provide ktime_get_raw()
hangcheck-timer: Use ktime_get_ns()
...
Diffstat (limited to 'include/linux/seqlock.h')
-rw-r--r-- | include/linux/seqlock.h | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index 8cf350325dc6..cc359636cfa3 100644 --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -117,6 +117,22 @@ repeat: } /** + * raw_read_seqcount - Read the raw seqcount + * @s: pointer to seqcount_t + * Returns: count to be passed to read_seqcount_retry + * + * raw_read_seqcount opens a read critical section of the given + * seqcount without any lockdep checking and without checking or + * masking the LSB. Calling code is responsible for handling that. + */ +static inline unsigned raw_read_seqcount(const seqcount_t *s) +{ + unsigned ret = ACCESS_ONCE(s->sequence); + smp_rmb(); + return ret; +} + +/** * raw_read_seqcount_begin - start seq-read critical section w/o lockdep * @s: pointer to seqcount_t * Returns: count to be passed to read_seqcount_retry @@ -218,6 +234,17 @@ static inline void raw_write_seqcount_end(seqcount_t *s) } /* + * raw_write_seqcount_latch - redirect readers to even/odd copy + * @s: pointer to seqcount_t + */ +static inline void raw_write_seqcount_latch(seqcount_t *s) +{ + smp_wmb(); /* prior stores before incrementing "sequence" */ + s->sequence++; + smp_wmb(); /* increment "sequence" before following stores */ +} + +/* * Sequence counter only version assumes that callers are using their * own mutexing. */ |