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| author | David S. Miller <davem@davemloft.net> | 2017-07-21 05:38:43 +0300 |
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| committer | David S. Miller <davem@davemloft.net> | 2017-07-21 05:38:43 +0300 |
| commit | 7a68ada6ec7d88c68057d3a4c2a517eb94289976 (patch) | |
| tree | 51cd586e74fc92bfbdf382fa1544a235d908b25c /Documentation/pi-futex.txt | |
| parent | 760446f967678e14ee1b6464ee1bb8562f299fa6 (diff) | |
| parent | 96080f697786e0a30006fcbcc5b53f350fcb3e9f (diff) | |
| download | linux-7a68ada6ec7d88c68057d3a4c2a517eb94289976.tar.xz | |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Diffstat (limited to 'Documentation/pi-futex.txt')
| -rw-r--r-- | Documentation/pi-futex.txt | 15 |
1 files changed, 8 insertions, 7 deletions
diff --git a/Documentation/pi-futex.txt b/Documentation/pi-futex.txt index 9a5bc8651c29..aafddbee7377 100644 --- a/Documentation/pi-futex.txt +++ b/Documentation/pi-futex.txt @@ -1,5 +1,6 @@ +====================== Lightweight PI-futexes ----------------------- +====================== We are calling them lightweight for 3 reasons: @@ -25,8 +26,8 @@ determinism and well-bound latencies. Even in the worst-case, PI will improve the statistical distribution of locking related application delays. -The longer reply: ------------------ +The longer reply +---------------- Firstly, sharing locks between multiple tasks is a common programming technique that often cannot be replaced with lockless algorithms. As we @@ -71,8 +72,8 @@ deterministic execution of the high-prio task: any medium-priority task could preempt the low-prio task while it holds the shared lock and executes the critical section, and could delay it indefinitely. -Implementation: ---------------- +Implementation +-------------- As mentioned before, the userspace fastpath of PI-enabled pthread mutexes involves no kernel work at all - they behave quite similarly to @@ -83,8 +84,8 @@ entering the kernel. To handle the slowpath, we have added two new futex ops: - FUTEX_LOCK_PI - FUTEX_UNLOCK_PI + - FUTEX_LOCK_PI + - FUTEX_UNLOCK_PI If the lock-acquire fastpath fails, [i.e. an atomic transition from 0 to TID fails], then FUTEX_LOCK_PI is called. The kernel does all the |