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lib_pathbuffer.c:Use atomic instead of locks

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Summary:
  Use atomic_cmpxchg to ensure that in multithreaded situations, if someone releases the buffer, it can be applied for in time. And use atomic_ulong to save free_bitmap

Signed-off-by: chenrun1 <chenrun1@xiaomi.com>
This commit is contained in:
chenrun1 2024-12-11 17:52:17 +08:00 committed by Xiang Xiao
parent 4c379ecc98
commit 9138e8af01
1 changed files with 21 additions and 26 deletions
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47
libs/libc/misc/lib_pathbuffer.c
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@ -25,7 +25,7 @@
****************************************************************************/ ****************************************************************************/
#include <nuttx/config.h> #include <nuttx/config.h>
#include <nuttx/spinlock.h> #include <nuttx/atomic.h>
#include <nuttx/lib/lib.h> #include <nuttx/lib/lib.h>
#include <stdlib.h> #include <stdlib.h>
@ -41,8 +41,7 @@
struct pathbuffer_s struct pathbuffer_s
{ {
spinlock_t lock; /* Lock for the buffer */ atomic_t free_bitmap; /* Bitmap of free buffer */
unsigned long free_bitmap; /* Bitmap of free buffer */
char buffer[CONFIG_LIBC_PATHBUFFER_MAX][PATH_MAX]; char buffer[CONFIG_LIBC_PATHBUFFER_MAX][PATH_MAX];
}; };
@ -52,7 +51,6 @@ struct pathbuffer_s
static struct pathbuffer_s g_pathbuffer = static struct pathbuffer_s g_pathbuffer =
{ {
SP_UNLOCKED,
(1u << CONFIG_LIBC_PATHBUFFER_MAX) - 1, (1u << CONFIG_LIBC_PATHBUFFER_MAX) - 1,
}; };
@ -82,21 +80,23 @@ static struct pathbuffer_s g_pathbuffer =
FAR char *lib_get_pathbuffer(void) FAR char *lib_get_pathbuffer(void)
{ {
irqstate_t flags; for (; ; )
int index;
/* Try to find a free buffer */
flags = spin_lock_irqsave(&g_pathbuffer.lock);
index = ffsl(g_pathbuffer.free_bitmap) - 1;
if (index >= 0 && index < CONFIG_LIBC_PATHBUFFER_MAX)
{ {
g_pathbuffer.free_bitmap &= ~(1u << index); int32_t update;
spin_unlock_irqrestore(&g_pathbuffer.lock, flags); int32_t free_bitmap = atomic_read(&g_pathbuffer.free_bitmap);
return g_pathbuffer.buffer[index]; int index = ffsl(free_bitmap) - 1;
} if (index < 0 || index >= CONFIG_LIBC_PATHBUFFER_MAX)
{
break;
}
spin_unlock_irqrestore(&g_pathbuffer.lock, flags); update = free_bitmap & ~(1u << index);
if (atomic_cmpxchg(&g_pathbuffer.free_bitmap, &free_bitmap,
update))
{
return g_pathbuffer.buffer[index];
}
}
/* If no free buffer is found, allocate a new one if /* If no free buffer is found, allocate a new one if
* CONFIG_LIBC_PATHBUFFER_MALLOC is enabled * CONFIG_LIBC_PATHBUFFER_MALLOC is enabled
@ -125,17 +125,12 @@ FAR char *lib_get_pathbuffer(void)
void lib_put_pathbuffer(FAR char *buffer) void lib_put_pathbuffer(FAR char *buffer)
{ {
irqstate_t flags; int index = (buffer - &g_pathbuffer.buffer[0][0]) / PATH_MAX;
int index;
index = (buffer - &g_pathbuffer.buffer[0][0]) / PATH_MAX;
if (index >= 0 && index < CONFIG_LIBC_PATHBUFFER_MAX) if (index >= 0 && index < CONFIG_LIBC_PATHBUFFER_MAX)
{ {
/* Mark the corresponding bit as free */ DEBUGASSERT((atomic_read(&g_pathbuffer.free_bitmap) &
(1u << index)) == 0);
flags = spin_lock_irqsave(&g_pathbuffer.lock); atomic_fetch_or_acquire(&g_pathbuffer.free_bitmap, 1u << index);
g_pathbuffer.free_bitmap |= 1u << index;
spin_unlock_irqrestore(&g_pathbuffer.lock, flags);
return; return;
} }