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Logger: don't drop log messages at high priority. #1633

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Merged
kareltucek merged 1 commit into from
Sep 30, 2026
Merged

Logger: don't drop log messages at high priority. #1633

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3 changes: 3 additions & 0 deletions device/src/logger_priority.c
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Original file line number Diff line number Diff line change
Expand Up @@ -62,7 +62,10 @@ int set_thread_priority_by_name(const char *thread_name, int new_priority) {
#define LOG_THREAD_PRIORITY_HIGH K_PRIO_COOP(CONFIG_NUM_COOP_PRIORITIES - 1)
#define LOG_THREAD_PRIORITY_LOW K_PRIO_PREEMPT(K_LOWEST_APPLICATION_THREAD_PRIO - 1)

bool Logger_PriorityHigh = false;

void Logger_SetPriority(bool high) {
Logger_PriorityHigh = high;
set_thread_priority_by_name("logging", high ? LOG_THREAD_PRIORITY_HIGH : LOG_THREAD_PRIORITY_LOW);
set_thread_priority_by_name("UhkShell", SHELL_THREAD_PRIORITY);
set_thread_priority_by_name("shell_rtt", SHELL_THREAD_PRIORITY);
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3 changes: 3 additions & 0 deletions device/src/logger_priority.h
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Expand Up @@ -15,6 +15,9 @@

// Functions:

// True while the logging thread runs at high priority (see Logger_SetPriority).
extern bool Logger_PriorityHigh;

void Logger_SetPriority(bool high);

#endif // __MAIN_H__
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25 changes: 25 additions & 0 deletions right/src/logger.c
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Expand Up @@ -23,6 +23,7 @@
#include <zephyr/logging/log_ctrl.h>
#include <zephyr/shell/shell.h>
#include <zephyr/shell/shell_uart.h>
#include "logger_priority.h"
#if DEVICE_IS_KEYBOARD
#include "keyboard/uart_bridge.h"
#ifdef DEVICE_HAS_OLED
Expand All @@ -47,6 +48,24 @@ char BUFFER[MAX_LOG_LENGTH]; \
BUFFER[MAX_LOG_LENGTH-1] = '\0'; \
}

#ifdef __ZEPHYR__
// With the logging thread at high priority, thread-context producers wait for the deferred
// log buffer to drain instead of overflowing it (the buffer overwrites its oldest messages).
// ISR-context producers cannot wait and may still drop. Bounded, so a stalled log thread
// can't hang callers. Must not run inside a REENTRANCY_GUARD - it drops concurrent logs.
#define LOG_BACKPRESSURE_MAX_BUFFERED 8
#define LOG_BACKPRESSURE_MAX_WAIT_MS 50

static void uartLogBackpressure(void) {
if (Logger_PriorityHigh && !k_is_in_isr()) {
for (uint8_t i = 0; i < LOG_BACKPRESSURE_MAX_WAIT_MS && log_buffered_cnt() > LOG_BACKPRESSURE_MAX_BUFFERED; i++) {
log_thread_trigger();
k_msleep(1);
}
}
}
#endif

void Uart_LogConstant(const char* buffer) {
#ifdef __ZEPHYR__
printk("%s", buffer);
Expand All @@ -57,6 +76,7 @@ void Uart_Log(const char *fmt, ...) {
#ifdef __ZEPHYR__
EXPAND_STRING(buffer);

uartLogBackpressure();
Uart_LogConstant(buffer);
#endif
}
Expand Down Expand Up @@ -165,6 +185,11 @@ void LogUSDO(const char *fmt, ...) {
}

void LogConstantTo(device_id_t deviceId, log_target_t logMask, const char* buffer) {
#ifdef __ZEPHYR__
if ((logMask & LogTarget_Uart) && DEBUG_LOG_UART && (DEVICE_IS_UHK60 || DEVICE_ID == deviceId)) {
uartLogBackpressure();
}
#endif
REENTRANCY_GUARD_BEGIN;
if (DEVICE_IS_UHK60 || DEVICE_ID == deviceId) {
#if DEVICE_HAS_OLED
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