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rp2_sd: Fix race window in sd_spi_wait_complete

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Similar to the fix in 6f155ebb55 ("audiocore: Fix small race window in
get_fifo_read_value_blocking"), a race and deadlock is possible when
calling __wfi with interrupts enabled. Fix it in sd_spi_wait_complete by
copying the fix from the above commit.

Signed-off-by: Matthias Blankertz <matthias@blankertz.org>
This commit is contained in:
Matthias Blankertz
2025-10-27 21:13:48 +01:00
parent 231172f794
commit 2a4033d3ca
1 changed files with 14 additions and 2 deletions
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16
software/modules/rp2_sd/sd_spi.c
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@@ -12,13 +12,15 @@
#include <pico/time.h> #include <pico/time.h>
#include <string.h> #include <string.h>
typedef enum { DMA_READ_TOKEN, DMA_READ, DMA_IDLE } sd_dma_state;
struct sd_dma_context { struct sd_dma_context {
uint8_t *read_buf; uint8_t *read_buf;
size_t len; size_t len;
uint8_t crc_buf[2]; uint8_t crc_buf[2];
uint8_t read_token_buf; uint8_t read_token_buf;
uint8_t wrdata; uint8_t wrdata;
_Atomic enum { DMA_READ_TOKEN, DMA_READ, DMA_IDLE } state; _Atomic sd_dma_state state;
}; };
struct sd_spi_context { struct sd_spi_context {
@@ -111,8 +113,18 @@ static void __time_critical_func(sd_spi_dma_isr)(void)
void sd_spi_wait_complete(void) void sd_spi_wait_complete(void)
{ {
while (sd_spi_context.sd_dma_context.state != DMA_IDLE) while (true) {
const long flags = save_and_disable_interrupts();
const sd_dma_state state = sd_spi_context.sd_dma_context.state;
if (state == DMA_IDLE) {
restore_interrupts(flags);
return;
}
__wfi(); __wfi();
restore_interrupts(flags);
__nop(); // Ensure at least two instructions between enable interrupts and subsequent disable
__nop();
}
} }
bool sd_cmd_read_is_complete(void) { return sd_spi_context.sd_dma_context.state == DMA_IDLE; } bool sd_cmd_read_is_complete(void) { return sd_spi_context.sd_dma_context.state == DMA_IDLE; }