diff options
Diffstat (limited to 'debian/patches-rt/0084-printk-Reduce-pr_flush-pooling-time.patch')
| -rw-r--r-- | debian/patches-rt/0084-printk-Reduce-pr_flush-pooling-time.patch | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/debian/patches-rt/0084-printk-Reduce-pr_flush-pooling-time.patch b/debian/patches-rt/0084-printk-Reduce-pr_flush-pooling-time.patch new file mode 100644 index 0000000000..09d1d343f4 --- /dev/null +++ b/debian/patches-rt/0084-printk-Reduce-pr_flush-pooling-time.patch @@ -0,0 +1,102 @@ +From: Petr Mladek <pmladek@suse.com> +Date: Fri, 6 Oct 2023 10:21:51 +0200 +Subject: [PATCH 084/134] printk: Reduce pr_flush() pooling time +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz + +pr_flush() does not guarantee that all messages would really get flushed +to the console. The best it could do is to wait with a given timeout.[*] + +The current interval 100ms for checking the progress might seem too +long in some situations. For example, such delays are not appreciated +during suspend and resume especially when the consoles have been flushed +"long" time before the check. + +On the other hand, the sleeping wait might be useful in other situations. +Especially, it would allow flushing the messages using printk kthreads +on the same CPU[*]. + +Use msleep(1) as a compromise. + +Also measure the time using jiffies. msleep() does not guarantee +precise wakeup after the given delay. It might be much longer, +especially for times < 20s. See Documentation/timers/timers-howto.rst +for more details. + +Note that msecs_to_jiffies() already translates a negative value into +an infinite timeout. + +[*] console_unlock() does not guarantee flushing the consoles since + the commit dbdda842fe96f893 ("printk: Add console owner and waiter + logic to load balance console writes"). + + It would be possible to guarantee it another way. For example, + the spinning might be enabled only when the console_lock has been + taken via console_trylock(). + + But the load balancing is helpful. And more importantly, the flush + with a timeout has been added as a preparation step for introducing + printk kthreads. + +Signed-off-by: Petr Mladek <pmladek@suse.com> +Reviewed-by: John Ogness <john.ogness@linutronix.de> +Link: https://lore.kernel.org/r/20231006082151.6969-3-pmladek@suse.com +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + kernel/printk/printk.c | 26 +++++++++++++------------- + 1 file changed, 13 insertions(+), 13 deletions(-) + +--- a/kernel/printk/printk.c ++++ b/kernel/printk/printk.c +@@ -3742,7 +3742,8 @@ late_initcall(printk_late_init); + /* If @con is specified, only wait for that console. Otherwise wait for all. */ + static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) + { +- int remaining = timeout_ms; ++ unsigned long timeout_jiffies = msecs_to_jiffies(timeout_ms); ++ unsigned long remaining_jiffies = timeout_jiffies; + struct console *c; + u64 last_diff = 0; + u64 printk_seq; +@@ -3760,6 +3761,9 @@ static bool __pr_flush(struct console *c + console_unlock(); + + for (;;) { ++ unsigned long begin_jiffies; ++ unsigned long slept_jiffies; ++ + diff = 0; + + /* +@@ -3797,24 +3801,20 @@ static bool __pr_flush(struct console *c + console_srcu_read_unlock(cookie); + + if (diff != last_diff && reset_on_progress) +- remaining = timeout_ms; ++ remaining_jiffies = timeout_jiffies; + + console_unlock(); + + /* Note: @diff is 0 if there are no usable consoles. */ +- if (diff == 0 || remaining == 0) ++ if (diff == 0 || remaining_jiffies == 0) + break; + +- if (remaining < 0) { +- /* no timeout limit */ +- msleep(100); +- } else if (remaining < 100) { +- msleep(remaining); +- remaining = 0; +- } else { +- msleep(100); +- remaining -= 100; +- } ++ /* msleep(1) might sleep much longer. Check time by jiffies. */ ++ begin_jiffies = jiffies; ++ msleep(1); ++ slept_jiffies = jiffies - begin_jiffies; ++ ++ remaining_jiffies -= min(slept_jiffies, remaining_jiffies); + + last_diff = diff; + } |