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posix-timers: Add support for fd based clocks

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Extend the negative clockids which are currently used by posix cpu
timers to encode the PID with a file descriptor based type which
encodes the fd in the upper bits.

Originally-from: Richard Cochran <richard.cochran@omicron.at>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <20110201134420.062860200@linutronix.de>
This commit is contained in:
Richard Cochran 2011-02-01 13:52:32 +00:00 committed by Thomas Gleixner
parent ce26efdefa
commit 81e294cba2
2 changed files with 14 additions and 1 deletions
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13
include/linux/posix-timers.h
View File

@ -18,6 +18,17 @@ struct cpu_timer_list {
int firing;
};
/*
* Bit fields within a clockid:
*
* The most significant 29 bits hold either a pid or a file descriptor.
*
* Bit 2 indicates whether a cpu clock refers to a thread or a process.
*
* Bits 1 and 0 give the type: PROF=0, VIRT=1, SCHED=2, or FD=3.
*
* A clockid is invalid if bits 2, 1, and 0 are all set.
*/
#define CPUCLOCK_PID(clock) ((pid_t) ~((clock) >> 3))
#define CPUCLOCK_PERTHREAD(clock) \
(((clock) & (clockid_t) CPUCLOCK_PERTHREAD_MASK) != 0)
@ -29,6 +40,8 @@ struct cpu_timer_list {
#define CPUCLOCK_VIRT 1
#define CPUCLOCK_SCHED 2
#define CPUCLOCK_MAX 3
#define CLOCKFD CPUCLOCK_MAX
#define CLOCKFD_MASK (CPUCLOCK_PERTHREAD_MASK|CPUCLOCK_CLOCK_MASK)
#define MAKE_PROCESS_CPUCLOCK(pid, clock) \
((~(clockid_t) (pid) << 3) | (clockid_t) (clock))

2
kernel/posix-timers.c
View File

@ -488,7 +488,7 @@ static void release_posix_timer(struct k_itimer *tmr, int it_id_set)
static struct k_clock *clockid_to_kclock(const clockid_t id)
{
if (id < 0)
return &clock_posix_cpu;
return (id & CLOCKFD_MASK) == CLOCKFD ? NULL : &clock_posix_cpu;
if (id >= MAX_CLOCKS || !posix_clocks[id].clock_getres)
return NULL;