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x86: Simplify _IntVecAlloc() logic

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Instead of using logic choosing between invoking find_lsb_set() and
find_msb_set(), mask out the unwanted bits and always invoke find_lsb_set().
This also has the side benefit of simplifying the error checking when DEBUG is
enabled.

Change-Id: I7f3e529ab3807b4433291197793e79e371d06ae3
Signed-off-by: Peter Mitsis <peter.mitsis@windriver.com>
This commit is contained in:
Peter Mitsis 2015-09-30 13:07:53 -04:00 • committed by Anas Nashif
commit 3bcaad8a39
1 changed files with 22 additions and 45 deletions
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67
arch/x86/core/intconnect.c
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@ -496,11 +496,14 @@ int irq_connect(
int _IntVecAlloc(unsigned int priority)
{
unsigned int imask;
unsigned int key;
unsigned int entryToScan;
unsigned int fsb; /* first set bit in entry */
unsigned int search_set;
int vector;
static unsigned int mask[2] = {0x0000ffff, 0xffff0000};
#if defined(DEBUG)
/*
* check whether the IDT was configured with sufficient vectors to
@ -520,64 +523,38 @@ int _IntVecAlloc(unsigned int priority)
entryToScan = priority >> 1; /* interrupt_vectors_allocated[] entry to scan */
/*
* The interrupt_vectors_allocated[] entry specified by 'entryToScan' is a 32-bit
* quantity and thus represents the vectors for a pair of priority
*levels.
* Use find_msb_set() to scan for the upper of the 2, and find_lsb_set() to
*scan
* for the lower of the 2 priorities.
* The interrupt_vectors_allocated[] entry specified by 'entryToScan' is a
* 32-bit quantity and thus represents the vectors for a pair of priority
* levels. Mask out the unwanted priority level and then use find_lsb_set()
* to scan for an available vector of the requested priority.
*
* Note that find_lsb_set/find_msb_set returns bit position from 1 to 32,
* Note that find_lsb_set() returns bit position from 1 to 32,
* or 0 if the argument is zero.
*/
imask = irq_lock();
key = irq_lock();
if ((priority % 2) == 0) {
/* scan from the LSB for even priorities */
fsb = find_lsb_set(interrupt_vectors_allocated[entryToScan]);
search_set = mask[priority & 1] & interrupt_vectors_allocated[entryToScan];
fsb = find_lsb_set(search_set);
#if defined(DEBUG)
if ((fsb == 0) || (fsb > 16)) {
/*
* No bits are set in the lower 16 bits, thus all
* vectors for this
* priority have been allocated.
*/
if (fsb == 0) {
/* All vectors for this priority have been allocated. */
irq_unlock(imask);
return (-1);
}
#endif /* DEBUG */
} else {
/* scan from the MSB for odd priorities */
fsb = find_msb_set(interrupt_vectors_allocated[entryToScan]);
#if defined(DEBUG)
if ((fsb == 0) || (fsb < 17)) {
/*
* No bits are set in the lower 16 bits, thus all
* vectors for this
* priority have been allocated.
*/
irq_unlock(imask);
return (-1);
}
#endif /* DEBUG */
irq_unlock(key);
return (-1);
}
#endif /* DEBUG */
/* ffsLsb/ffsMsb returns bit positions as 1 to 32 */
/*
* An available vector of the requested priority was found.
* Mark it as allocated.
*/
--fsb;
/* mark the vector as allocated */
interrupt_vectors_allocated[entryToScan] &= ~(1 << fsb);
irq_unlock(imask);
irq_unlock(key);
/* compute vector given allocated bit within the priority level */