diff options
Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0206-printk-Make-rt-aware.patch | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/debian/patches-rt/0206-printk-Make-rt-aware.patch b/debian/patches-rt/0206-printk-Make-rt-aware.patch new file mode 100644 index 000000000..0ca16f202 --- /dev/null +++ b/debian/patches-rt/0206-printk-Make-rt-aware.patch @@ -0,0 +1,114 @@ +From fe512f6331aa2cda166c08988965010dd06d68e3 Mon Sep 17 00:00:00 2001 +From: Thomas Gleixner <tglx@linutronix.de> +Date: Wed, 19 Sep 2012 14:50:37 +0200 +Subject: [PATCH 206/347] printk: Make rt aware +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz + +Drop the lock before calling the console driver and do not disable +interrupts while printing to a serial console. + +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +--- + kernel/printk/printk.c | 33 ++++++++++++++++++++++++++++++--- + 1 file changed, 30 insertions(+), 3 deletions(-) + +diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c +index 7b774743e1ac..c06b1e00448d 100644 +--- a/kernel/printk/printk.c ++++ b/kernel/printk/printk.c +@@ -1654,6 +1654,7 @@ SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len) + return do_syslog(type, buf, len, SYSLOG_FROM_READER); + } + ++#ifndef CONFIG_PREEMPT_RT_FULL + /* + * Special console_lock variants that help to reduce the risk of soft-lockups. + * They allow to pass console_lock to another printk() call using a busy wait. +@@ -1794,6 +1795,15 @@ static int console_trylock_spinning(void) + return 1; + } + ++#else ++ ++static int console_trylock_spinning(void) ++{ ++ return console_trylock(); ++} ++ ++#endif ++ + /* + * Call the console drivers, asking them to write out + * log_buf[start] to log_buf[end - 1]. +@@ -1809,6 +1819,7 @@ static void call_console_drivers(const char *ext_text, size_t ext_len, + if (!console_drivers) + return; + ++ migrate_disable(); + for_each_console(con) { + if (exclusive_console && con != exclusive_console) + continue; +@@ -1824,6 +1835,7 @@ static void call_console_drivers(const char *ext_text, size_t ext_len, + else + con->write(con, text, len); + } ++ migrate_enable(); + } + + int printk_delay_msec __read_mostly; +@@ -2018,20 +2030,30 @@ asmlinkage int vprintk_emit(int facility, int level, + + /* If called from the scheduler, we can not call up(). */ + if (!in_sched && pending_output) { ++ int may_trylock = 1; ++ ++#ifdef CONFIG_PREEMPT_RT_FULL ++ /* ++ * we can't take a sleeping lock with IRQs or preeption disabled ++ * so we can't print in these contexts ++ */ ++ if (!(preempt_count() == 0 && !irqs_disabled())) ++ may_trylock = 0; ++#endif + /* + * Disable preemption to avoid being preempted while holding + * console_sem which would prevent anyone from printing to + * console + */ +- preempt_disable(); ++ migrate_disable(); + /* + * Try to acquire and then immediately release the console + * semaphore. The release will print out buffers and wake up + * /dev/kmsg and syslog() users. + */ +- if (console_trylock_spinning()) ++ if (may_trylock && console_trylock_spinning()) + console_unlock(); +- preempt_enable(); ++ migrate_enable(); + } + + if (pending_output) +@@ -2503,6 +2525,10 @@ void console_unlock(void) + console_seq++; + raw_spin_unlock(&logbuf_lock); + ++#ifdef CONFIG_PREEMPT_RT_FULL ++ printk_safe_exit_irqrestore(flags); ++ call_console_drivers(ext_text, ext_len, text, len); ++#else + /* + * While actively printing out messages, if another printk() + * were to occur on another CPU, it may wait for this one to +@@ -2521,6 +2547,7 @@ void console_unlock(void) + } + + printk_safe_exit_irqrestore(flags); ++#endif + + if (do_cond_resched) + cond_resched(); +-- +2.36.1 + |