118 lines
3.5 KiB
Diff
118 lines
3.5 KiB
Diff
From 99abb977ad29a00172612acdcd8cf3fbe95470b4 Mon Sep 17 00:00:00 2001
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Message-Id: <99abb977ad29a00172612acdcd8cf3fbe95470b4.1601675152.git.zanussi@kernel.org>
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In-Reply-To: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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References: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Wed, 19 Sep 2012 14:50:37 +0200
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Subject: [PATCH 206/333] printk: Make rt aware
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.148-rt64.tar.xz
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Drop the lock before calling the console driver and do not disable
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interrupts while printing to a serial console.
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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kernel/printk/printk.c | 33 ++++++++++++++++++++++++++++++---
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1 file changed, 30 insertions(+), 3 deletions(-)
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diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
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index e582817249ce..1eb212298f95 100644
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--- a/kernel/printk/printk.c
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+++ b/kernel/printk/printk.c
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@@ -1652,6 +1652,7 @@ SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
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return do_syslog(type, buf, len, SYSLOG_FROM_READER);
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}
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+#ifndef CONFIG_PREEMPT_RT_FULL
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/*
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* Special console_lock variants that help to reduce the risk of soft-lockups.
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* They allow to pass console_lock to another printk() call using a busy wait.
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@@ -1792,6 +1793,15 @@ static int console_trylock_spinning(void)
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return 1;
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}
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+#else
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+
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+static int console_trylock_spinning(void)
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+{
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+ return console_trylock();
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+}
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+
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+#endif
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+
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/*
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* Call the console drivers, asking them to write out
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* log_buf[start] to log_buf[end - 1].
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@@ -1807,6 +1817,7 @@ static void call_console_drivers(const char *ext_text, size_t ext_len,
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if (!console_drivers)
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return;
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+ migrate_disable();
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for_each_console(con) {
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if (exclusive_console && con != exclusive_console)
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continue;
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@@ -1822,6 +1833,7 @@ static void call_console_drivers(const char *ext_text, size_t ext_len,
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else
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con->write(con, text, len);
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}
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+ migrate_enable();
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}
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int printk_delay_msec __read_mostly;
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@@ -2016,20 +2028,30 @@ asmlinkage int vprintk_emit(int facility, int level,
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/* If called from the scheduler, we can not call up(). */
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if (!in_sched && pending_output) {
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+ int may_trylock = 1;
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+
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+ /*
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+ * we can't take a sleeping lock with IRQs or preeption disabled
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+ * so we can't print in these contexts
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+ */
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+ if (!(preempt_count() == 0 && !irqs_disabled()))
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+ may_trylock = 0;
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+#endif
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/*
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* Disable preemption to avoid being preempted while holding
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* console_sem which would prevent anyone from printing to
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* console
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*/
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- preempt_disable();
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+ migrate_disable();
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/*
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* Try to acquire and then immediately release the console
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* semaphore. The release will print out buffers and wake up
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* /dev/kmsg and syslog() users.
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*/
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- if (console_trylock_spinning())
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+ if (may_trylock && console_trylock_spinning())
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console_unlock();
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- preempt_enable();
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+ migrate_enable();
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}
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if (pending_output)
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@@ -2491,6 +2513,10 @@ void console_unlock(void)
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console_seq++;
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raw_spin_unlock(&logbuf_lock);
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+ printk_safe_exit_irqrestore(flags);
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+ call_console_drivers(ext_text, ext_len, text, len);
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+#else
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/*
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* While actively printing out messages, if another printk()
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* were to occur on another CPU, it may wait for this one to
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@@ -2509,6 +2535,7 @@ void console_unlock(void)
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}
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printk_safe_exit_irqrestore(flags);
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+#endif
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if (do_cond_resched)
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cond_resched();
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--
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2.17.1
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