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[v6,09/17] lib: time: hook uthread_schedule() into udelay()

Message ID 20250418141114.2056981-10-jerome.forissier@linaro.org
State New
Headers show
Series Uthreads | expand

Commit Message

Jerome Forissier April 18, 2025, 2:09 p.m. UTC 
Introduce a uthread scheduling loop into udelay() when CONFIG_UTHREAD
is enabled. This means that any uthread calling into udelay() may yield
to uthread and be scheduled again later. There is no delay in the
scheduling loop because tests have shown that such a delay can have a
detrimental effect on the console (input drops characters).

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
---

(no changes since v1)

 lib/time.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)
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Patch

diff --git a/lib/time.c b/lib/time.c
index d88edafb196..0e9b079f9cf 100644
--- a/lib/time.c
+++ b/lib/time.c
@@ -17,6 +17,7 @@ 
 #include <asm/global_data.h>
 #include <asm/io.h>
 #include <linux/delay.h>
+#include <uthread.h>
 
 #ifndef CFG_WD_PERIOD
 # define CFG_WD_PERIOD	(10 * 1000 * 1000)	/* 10 seconds default */
@@ -197,7 +198,13 @@  void udelay(unsigned long usec)
 	do {
 		schedule();
 		kv = usec > CFG_WD_PERIOD ? CFG_WD_PERIOD : usec;
-		__udelay(kv);
+		if (CONFIG_IS_ENABLED(UTHREAD)) {
+			ulong t0 = timer_get_us();
+			while (timer_get_us() - t0 < kv)
+				uthread_schedule();
+		} else {
+			__udelay(kv);
+		}
 		usec -= kv;
 	} while(usec);
 }