| From | Thomas Schoebel-Theuer <> | Subject | [PATCH 02/50] mars: add new file drivers/block/mars/lamport.c | Date | Tue, 1 Jul 2014 23:46:42 +0200 |
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Signed-off-by: Thomas Schoebel-Theuer <tst@schoebel-theuer.de> --- drivers/block/mars/lamport.c | 48 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 drivers/block/mars/lamport.c
diff --git a/drivers/block/mars/lamport.c b/drivers/block/mars/lamport.c new file mode 100644 index 0000000..67484c5 --- /dev/null +++ b/drivers/block/mars/lamport.c @@ -0,0 +1,48 @@ +/* (c) 2010 Thomas Schoebel-Theuer / 1&1 Internet AG */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/semaphore.h> + +#include <linux/brick/lamport.h> + +/* TODO: replace with spinlock if possible (first check) */ +struct semaphore lamport_sem = __SEMAPHORE_INITIALIZER(lamport_sem, 1); +struct timespec lamport_now = {}; + +void get_lamport(struct timespec *now) +{ + int diff; + + down(&lamport_sem); + + *now = CURRENT_TIME; + diff = timespec_compare(now, &lamport_now); + if (diff >= 0) { + timespec_add_ns(now, 1); + memcpy(&lamport_now, now, sizeof(lamport_now)); + timespec_add_ns(&lamport_now, 1); + } else { + timespec_add_ns(&lamport_now, 1); + memcpy(now, &lamport_now, sizeof(*now)); + } + + up(&lamport_sem); +} +EXPORT_SYMBOL_GPL(get_lamport); + +void set_lamport(struct timespec *old) +{ + int diff; + + down(&lamport_sem); + + diff = timespec_compare(old, &lamport_now); + if (diff >= 0) { + memcpy(&lamport_now, old, sizeof(lamport_now)); + timespec_add_ns(&lamport_now, 1); + } + + up(&lamport_sem); +} +EXPORT_SYMBOL_GPL(set_lamport); -- 2.0.0
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