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UISimulator: Need a 'while' not an 'if' in sim_enter_irq_handler. Add comments explaining things.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@28916 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Michael Sevakis 2010-12-28 11:33:55 +00:00
parent 1f06ca41e8
commit 4d39c9fb2e
1 changed files with 14 additions and 5 deletions
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19
firmware/target/hosted/sdl/kernel-sdl.c
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@ -39,8 +39,14 @@ static SDL_cond *sim_thread_cond;
/* Mutex to serialize changing levels and exclude other threads while
* inside a handler */
static SDL_mutex *sim_irq_mtx;
/* Level: 0 = enabled, not 0 = disabled */
static int interrupt_level = HIGHEST_IRQ_LEVEL;
/* How many handers waiting? Not strictly needed because CondSignal is a
* noop if no threads were waiting but it filters-out calls to functions
* with higher overhead and provides info when debugging. */
static int handlers_pending = 0;
/* 1 = executing a handler; prevents CondSignal calls in set_irq_level
* while in a handler */
static int status_reg = 0;
/* Nescessary logic:
@ -57,7 +63,8 @@ int set_irq_level(int level)
if (status_reg == 0 && level == 0 && oldlevel != 0)
{
/* Not in a handler and "interrupts" are being reenabled */
/* Not in a handler and "interrupts" are going from disabled to
* enabled; signal any pending handlers still waiting */
if (handlers_pending > 0)
SDL_CondSignal(sim_thread_cond);
}
@ -73,17 +80,19 @@ void sim_enter_irq_handler(void)
SDL_LockMutex(sim_irq_mtx);
handlers_pending++;
if(interrupt_level != 0)
{
/* "Interrupts" are disabled. Wait for reenable */
/* Check each time before proceeding: disabled->enabled->...->disabled
* is possible on an app thread before a handler thread is ever granted
* the mutex; a handler can also leave "interrupts" disabled during
* its execution */
while (interrupt_level != 0)
SDL_CondWait(sim_thread_cond, sim_irq_mtx);
}
status_reg = 1;
}
void sim_exit_irq_handler(void)
{
/* If any others are waiting, give the signal */
if (--handlers_pending > 0)
SDL_CondSignal(sim_thread_cond);