diff options
Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0024-printk-nbcon-Add-unsafe-flushing-on-panic.patch | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/debian/patches-rt/0024-printk-nbcon-Add-unsafe-flushing-on-panic.patch b/debian/patches-rt/0024-printk-nbcon-Add-unsafe-flushing-on-panic.patch new file mode 100644 index 0000000000..a63a8ac515 --- /dev/null +++ b/debian/patches-rt/0024-printk-nbcon-Add-unsafe-flushing-on-panic.patch @@ -0,0 +1,125 @@ +From: John Ogness <john.ogness@linutronix.de> +Date: Fri, 20 Oct 2023 10:03:42 +0000 +Subject: [PATCH 24/48] printk: nbcon: Add unsafe flushing on panic +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.8/older/patches-6.8.2-rt11.tar.xz + +Add nbcon_atomic_flush_unsafe() to flush all nbcon consoles +using the write_atomic() callback and allowing unsafe hostile +takeovers. Call this at the end of panic() as a final attempt +to flush any pending messages. + +Note that legacy consoles use unsafe methods for flushing +from the beginning of panic (see bust_spinlocks()). Therefore, +systems using both legacy and nbcon consoles may still fail to +see panic messages due to unsafe legacy console usage. + +Signed-off-by: John Ogness <john.ogness@linutronix.de> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + include/linux/printk.h | 5 +++++ + kernel/panic.c | 1 + + kernel/printk/nbcon.c | 26 +++++++++++++++++++++----- + 3 files changed, 27 insertions(+), 5 deletions(-) + +--- a/include/linux/printk.h ++++ b/include/linux/printk.h +@@ -197,6 +197,7 @@ extern asmlinkage void dump_stack(void) + void printk_trigger_flush(void); + extern void nbcon_driver_acquire(struct console *con); + extern void nbcon_driver_release(struct console *con); ++void nbcon_atomic_flush_unsafe(void); + #else + static inline __printf(1, 0) + int vprintk(const char *s, va_list args) +@@ -285,6 +286,10 @@ static inline void nbcon_driver_release( + { + } + ++static inline void nbcon_atomic_flush_unsafe(void) ++{ ++} ++ + #endif + + bool this_cpu_in_panic(void); +--- a/kernel/panic.c ++++ b/kernel/panic.c +@@ -453,6 +453,7 @@ void panic(const char *fmt, ...) + * Explicitly flush the kernel log buffer one last time. + */ + console_flush_on_panic(CONSOLE_FLUSH_PENDING); ++ nbcon_atomic_flush_unsafe(); + + local_irq_enable(); + for (i = 0; ; i += PANIC_TIMER_STEP) { +--- a/kernel/printk/nbcon.c ++++ b/kernel/printk/nbcon.c +@@ -1033,6 +1033,7 @@ bool nbcon_legacy_emit_next_record(struc + * write_atomic() callback + * @con: The nbcon console to flush + * @stop_seq: Flush up until this record ++ * @allow_unsafe_takeover: True, to allow unsafe hostile takeovers + * + * Return: True if taken over while printing. Otherwise false. + * +@@ -1041,7 +1042,8 @@ bool nbcon_legacy_emit_next_record(struc + * there are no more records available to read or this context is not allowed + * to acquire the console. + */ +-static bool __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq) ++static bool __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq, ++ bool allow_unsafe_takeover) + { + struct nbcon_write_context wctxt = { }; + struct nbcon_context *ctxt = &ACCESS_PRIVATE(&wctxt, ctxt); +@@ -1049,6 +1051,7 @@ static bool __nbcon_atomic_flush_pending + ctxt->console = con; + ctxt->spinwait_max_us = 2000; + ctxt->prio = nbcon_get_default_prio(); ++ ctxt->allow_unsafe_takeover = allow_unsafe_takeover; + + if (!nbcon_context_try_acquire(ctxt)) + return false; +@@ -1075,8 +1078,9 @@ static bool __nbcon_atomic_flush_pending + * __nbcon_atomic_flush_pending - Flush all nbcon consoles using their + * write_atomic() callback + * @stop_seq: Flush up until this record ++ * @allow_unsafe_takeover: True, to allow unsafe hostile takeovers + */ +-static void __nbcon_atomic_flush_pending(u64 stop_seq) ++static void __nbcon_atomic_flush_pending(u64 stop_seq, bool allow_unsafe_takeover) + { + struct console *con; + bool should_retry; +@@ -1109,8 +1113,8 @@ static void __nbcon_atomic_flush_pending + */ + local_irq_save(irq_flags); + +- should_retry |= __nbcon_atomic_flush_pending_con(con, stop_seq); +- ++ should_retry |= __nbcon_atomic_flush_pending_con(con, stop_seq, ++ allow_unsafe_takeover); + local_irq_restore(irq_flags); + } + console_srcu_read_unlock(cookie); +@@ -1127,7 +1131,19 @@ static void __nbcon_atomic_flush_pending + */ + void nbcon_atomic_flush_pending(void) + { +- __nbcon_atomic_flush_pending(prb_next_reserve_seq(prb)); ++ __nbcon_atomic_flush_pending(prb_next_reserve_seq(prb), false); ++} ++ ++/** ++ * nbcon_atomic_flush_unsafe - Flush all nbcon consoles using their ++ * write_atomic() callback and allowing unsafe hostile takeovers ++ * ++ * Flush the backlog up through the currently newest record. Unsafe hostile ++ * takeovers will be performed, if necessary. ++ */ ++void nbcon_atomic_flush_unsafe(void) ++{ ++ __nbcon_atomic_flush_pending(prb_next_reserve_seq(prb), true); + } + + /** |