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b24591e2fc
Add a function, similar to mod_timer(), that will start a timer if it isn't
running and will modify it if it is running and has an expiry time longer
than the new time. If the timer is running with an expiry time that's the
same or sooner, no change is made.
The function looks like:
int timer_reduce(struct timer_list *timer, unsigned long expires);
This can be used by code such as networking code to make it easier to share
a timer for multiple timeouts. For instance, in upcoming AF_RXRPC code,
the rxrpc_call struct will maintain a number of timeouts:
unsigned long ack_at;
unsigned long resend_at;
unsigned long ping_at;
unsigned long expect_rx_by;
unsigned long expect_req_by;
unsigned long expect_term_by;
each of which is set independently of the others. With timer reduction
available, when the code needs to set one of the timeouts, it only needs to
look at that timeout and then call timer_reduce() to modify the timer,
starting it or bringing it forward if necessary. There is no need to refer
to the other timeouts to see which is earliest and no need to take any lock
other than, potentially, the timer lock inside timer_reduce().
Note, that this does not protect against concurrent invocations of any of
the timer functions.
As an example, the expect_rx_by timeout above, which terminates a call if
we don't get a packet from the server within a certain time window, would
be set something like this:
unsigned long now = jiffies;
unsigned long expect_rx_by = now + packet_receive_timeout;
WRITE_ONCE(call->expect_rx_by, expect_rx_by);
timer_reduce(&call->timer, expect_rx_by);
The timer service code (which might, say, be in a work function) would then
check all the timeouts to see which, if any, had triggered, deal with
those:
t = READ_ONCE(call->ack_at);
if (time_after_eq(now, t)) {
cmpxchg(&call->ack_at, t, now + MAX_JIFFY_OFFSET);
set_bit(RXRPC_CALL_EV_ACK, &call->events);
}
and then restart the timer if necessary by finding the soonest timeout that
hasn't yet passed and then calling timer_reduce().
The disadvantage of doing things this way rather than comparing the timers
each time and calling mod_timer() is that you *will* take timer events
unless you can finish what you're doing and delete the timer in time.
The advantage of doing things this way is that you don't need to use a lock
to work out when the next timer should be set, other than the timer's own
lock - which you might not have to take.
[ tglx: Fixed weird formatting and adopted it to pending changes ]
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: keyrings@vger.kernel.org
Cc: linux-afs@lists.infradead.org
Link: https://lkml.kernel.org/r/151023090769.23050.1801643667223880753.stgit@warthog.procyon.org.uk
256 lines
8.3 KiB
C
256 lines
8.3 KiB
C
#ifndef _LINUX_TIMER_H
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#define _LINUX_TIMER_H
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#include <linux/list.h>
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#include <linux/ktime.h>
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#include <linux/stddef.h>
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#include <linux/debugobjects.h>
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#include <linux/stringify.h>
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struct tvec_base;
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struct timer_list {
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/*
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* All fields that change during normal runtime grouped to the
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* same cacheline
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*/
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struct hlist_node entry;
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unsigned long expires;
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void (*function)(unsigned long);
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unsigned long data;
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u32 flags;
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#ifdef CONFIG_LOCKDEP
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struct lockdep_map lockdep_map;
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#endif
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};
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#ifdef CONFIG_LOCKDEP
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/*
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* NB: because we have to copy the lockdep_map, setting the lockdep_map key
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* (second argument) here is required, otherwise it could be initialised to
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* the copy of the lockdep_map later! We use the pointer to and the string
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* "<file>:<line>" as the key resp. the name of the lockdep_map.
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*/
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#define __TIMER_LOCKDEP_MAP_INITIALIZER(_kn) \
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.lockdep_map = STATIC_LOCKDEP_MAP_INIT(_kn, &_kn),
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#else
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#define __TIMER_LOCKDEP_MAP_INITIALIZER(_kn)
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#endif
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/*
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* A deferrable timer will work normally when the system is busy, but
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* will not cause a CPU to come out of idle just to service it; instead,
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* the timer will be serviced when the CPU eventually wakes up with a
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* subsequent non-deferrable timer.
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*
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* An irqsafe timer is executed with IRQ disabled and it's safe to wait for
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* the completion of the running instance from IRQ handlers, for example,
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* by calling del_timer_sync().
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*
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* Note: The irq disabled callback execution is a special case for
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* workqueue locking issues. It's not meant for executing random crap
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* with interrupts disabled. Abuse is monitored!
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*/
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#define TIMER_CPUMASK 0x0003FFFF
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#define TIMER_MIGRATING 0x00040000
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#define TIMER_BASEMASK (TIMER_CPUMASK | TIMER_MIGRATING)
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#define TIMER_DEFERRABLE 0x00080000
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#define TIMER_PINNED 0x00100000
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#define TIMER_IRQSAFE 0x00200000
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#define TIMER_ARRAYSHIFT 22
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#define TIMER_ARRAYMASK 0xFFC00000
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#define TIMER_TRACE_FLAGMASK (TIMER_MIGRATING | TIMER_DEFERRABLE | TIMER_PINNED | TIMER_IRQSAFE)
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#define TIMER_DATA_TYPE unsigned long
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#define TIMER_FUNC_TYPE void (*)(TIMER_DATA_TYPE)
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#define __TIMER_INITIALIZER(_function, _data, _flags) { \
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.entry = { .next = TIMER_ENTRY_STATIC }, \
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.function = (_function), \
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.data = (_data), \
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.flags = (_flags), \
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__TIMER_LOCKDEP_MAP_INITIALIZER( \
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__FILE__ ":" __stringify(__LINE__)) \
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}
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#define DEFINE_TIMER(_name, _function) \
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struct timer_list _name = \
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__TIMER_INITIALIZER((TIMER_FUNC_TYPE)_function, 0, 0)
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void init_timer_key(struct timer_list *timer, unsigned int flags,
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const char *name, struct lock_class_key *key);
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#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
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extern void init_timer_on_stack_key(struct timer_list *timer,
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unsigned int flags, const char *name,
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struct lock_class_key *key);
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extern void destroy_timer_on_stack(struct timer_list *timer);
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#else
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static inline void destroy_timer_on_stack(struct timer_list *timer) { }
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static inline void init_timer_on_stack_key(struct timer_list *timer,
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unsigned int flags, const char *name,
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struct lock_class_key *key)
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{
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init_timer_key(timer, flags, name, key);
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}
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#endif
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#ifdef CONFIG_LOCKDEP
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#define __init_timer(_timer, _flags) \
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do { \
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static struct lock_class_key __key; \
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init_timer_key((_timer), (_flags), #_timer, &__key); \
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} while (0)
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#define __init_timer_on_stack(_timer, _flags) \
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do { \
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static struct lock_class_key __key; \
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init_timer_on_stack_key((_timer), (_flags), #_timer, &__key); \
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} while (0)
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#else
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#define __init_timer(_timer, _flags) \
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init_timer_key((_timer), (_flags), NULL, NULL)
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#define __init_timer_on_stack(_timer, _flags) \
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init_timer_on_stack_key((_timer), (_flags), NULL, NULL)
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#endif
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#define init_timer(timer) \
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__init_timer((timer), 0)
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#define __setup_timer(_timer, _fn, _data, _flags) \
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do { \
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__init_timer((_timer), (_flags)); \
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(_timer)->function = (_fn); \
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(_timer)->data = (_data); \
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} while (0)
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#define __setup_timer_on_stack(_timer, _fn, _data, _flags) \
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do { \
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__init_timer_on_stack((_timer), (_flags)); \
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(_timer)->function = (_fn); \
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(_timer)->data = (_data); \
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} while (0)
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#define setup_timer(timer, fn, data) \
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__setup_timer((timer), (fn), (data), 0)
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#define setup_pinned_timer(timer, fn, data) \
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__setup_timer((timer), (fn), (data), TIMER_PINNED)
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#define setup_deferrable_timer(timer, fn, data) \
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__setup_timer((timer), (fn), (data), TIMER_DEFERRABLE)
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#define setup_pinned_deferrable_timer(timer, fn, data) \
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__setup_timer((timer), (fn), (data), TIMER_DEFERRABLE | TIMER_PINNED)
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#define setup_timer_on_stack(timer, fn, data) \
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__setup_timer_on_stack((timer), (fn), (data), 0)
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#define setup_pinned_timer_on_stack(timer, fn, data) \
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__setup_timer_on_stack((timer), (fn), (data), TIMER_PINNED)
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#define setup_deferrable_timer_on_stack(timer, fn, data) \
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__setup_timer_on_stack((timer), (fn), (data), TIMER_DEFERRABLE)
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#define setup_pinned_deferrable_timer_on_stack(timer, fn, data) \
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__setup_timer_on_stack((timer), (fn), (data), TIMER_DEFERRABLE | TIMER_PINNED)
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#ifndef CONFIG_LOCKDEP
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static inline void timer_setup(struct timer_list *timer,
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void (*callback)(struct timer_list *),
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unsigned int flags)
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{
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__setup_timer(timer, (TIMER_FUNC_TYPE)callback,
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(TIMER_DATA_TYPE)timer, flags);
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}
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static inline void timer_setup_on_stack(struct timer_list *timer,
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void (*callback)(struct timer_list *),
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unsigned int flags)
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{
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__setup_timer_on_stack(timer, (TIMER_FUNC_TYPE)callback,
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(TIMER_DATA_TYPE)timer, flags);
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}
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#else
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/*
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* Under LOCKDEP, the timer lock_class_key (set up in __init_timer) needs
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* to be tied to the caller's context, so an inline (above) won't work. We
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* do want to keep the inline for argument type checking, though.
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*/
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# define timer_setup(timer, callback, flags) \
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__setup_timer((timer), (TIMER_FUNC_TYPE)(callback), \
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(TIMER_DATA_TYPE)(timer), (flags))
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# define timer_setup_on_stack(timer, callback, flags) \
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__setup_timer_on_stack((timer), \
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(TIMER_FUNC_TYPE)(callback), \
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(TIMER_DATA_TYPE)(timer), (flags))
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#endif
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#define from_timer(var, callback_timer, timer_fieldname) \
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container_of(callback_timer, typeof(*var), timer_fieldname)
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/**
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* timer_pending - is a timer pending?
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* @timer: the timer in question
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*
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* timer_pending will tell whether a given timer is currently pending,
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* or not. Callers must ensure serialization wrt. other operations done
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* to this timer, eg. interrupt contexts, or other CPUs on SMP.
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*
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* return value: 1 if the timer is pending, 0 if not.
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*/
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static inline int timer_pending(const struct timer_list * timer)
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{
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return timer->entry.pprev != NULL;
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}
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extern void add_timer_on(struct timer_list *timer, int cpu);
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extern int del_timer(struct timer_list * timer);
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extern int mod_timer(struct timer_list *timer, unsigned long expires);
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extern int mod_timer_pending(struct timer_list *timer, unsigned long expires);
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extern int timer_reduce(struct timer_list *timer, unsigned long expires);
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/*
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* The jiffies value which is added to now, when there is no timer
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* in the timer wheel:
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*/
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#define NEXT_TIMER_MAX_DELTA ((1UL << 30) - 1)
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extern void add_timer(struct timer_list *timer);
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extern int try_to_del_timer_sync(struct timer_list *timer);
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#ifdef CONFIG_SMP
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extern int del_timer_sync(struct timer_list *timer);
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#else
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# define del_timer_sync(t) del_timer(t)
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#endif
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#define del_singleshot_timer_sync(t) del_timer_sync(t)
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extern void init_timers(void);
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extern void run_local_timers(void);
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struct hrtimer;
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extern enum hrtimer_restart it_real_fn(struct hrtimer *);
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#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
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struct ctl_table;
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extern unsigned int sysctl_timer_migration;
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int timer_migration_handler(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos);
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#endif
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unsigned long __round_jiffies(unsigned long j, int cpu);
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unsigned long __round_jiffies_relative(unsigned long j, int cpu);
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unsigned long round_jiffies(unsigned long j);
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unsigned long round_jiffies_relative(unsigned long j);
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unsigned long __round_jiffies_up(unsigned long j, int cpu);
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unsigned long __round_jiffies_up_relative(unsigned long j, int cpu);
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unsigned long round_jiffies_up(unsigned long j);
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unsigned long round_jiffies_up_relative(unsigned long j);
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#ifdef CONFIG_HOTPLUG_CPU
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int timers_dead_cpu(unsigned int cpu);
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#else
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#define timers_dead_cpu NULL
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#endif
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#endif
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