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kernel: Remove B_TIMER_ACQUIRE_SCHEDULER_LOCK flag

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The flag main purpose is to avoid race conditions between event handler
and cancel_timer(). However, cancel_timer() is safe even without
using gSchedulerLock.

If the event is scheduled to happen on other CPU than the CPU that
invokes cancel_timer() then cancel_timer() either disables the event
before its handler starts executing or waits until the event handler
is done.

If the event is scheduled on the same CPU that calls cancel_timer()
then, since cancel_timer() disables interrupts, the event is either
executed before cancel_timer() or when the timer interrupt handler
starts running the event is already disabled.
This commit is contained in:
Pawel Dziepak
2013-10-31 01:49:43 +01:00
parent c8dd9f7780
commit d8fcc8a825
5 changed files with 12 additions and 56 deletions
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headers/private/kernel/timer.h
+1 -6
View File
@@ -23,13 +23,8 @@ struct kernel_args;
#define B_TIMER_USE_TIMER_STRUCT_TIMES 0x4000
// For add_timer(): Use the timer::schedule_time (absolute time) and
// timer::period values instead of the period parameter.
#define B_TIMER_ACQUIRE_SCHEDULER_LOCK 0x8000
// The timer hook is invoked with the scheduler lock held. When invoking
// cancel_timer() with the scheduler lock held, too, this helps to avoid
// race conditions.
#define B_TIMER_FLAGS \
(B_TIMER_USE_TIMER_STRUCT_TIMES | B_TIMER_ACQUIRE_SCHEDULER_LOCK \
| B_TIMER_REAL_TIME_BASE)
(B_TIMER_USE_TIMER_STRUCT_TIMES | B_TIMER_REAL_TIME_BASE)
/* Timer info structure */
struct timer_info {