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Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0021-printk-nbcon-Add-unsafe-flushing-on-panic.patch | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/debian/patches-rt/0021-printk-nbcon-Add-unsafe-flushing-on-panic.patch b/debian/patches-rt/0021-printk-nbcon-Add-unsafe-flushing-on-panic.patch new file mode 100644 index 0000000000..7b79f9d743 --- /dev/null +++ b/debian/patches-rt/0021-printk-nbcon-Add-unsafe-flushing-on-panic.patch @@ -0,0 +1,159 @@ +From: John Ogness <john.ogness@linutronix.de> +Date: Fri, 20 Oct 2023 10:03:42 +0000 +Subject: [PATCH 21/46] printk: nbcon: Add unsafe flushing on panic +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.9/older/patches-6.9-rt5.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> +Reviewed-by: Petr Mladek <pmladek@suse.com> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + include/linux/printk.h | 5 +++++ + kernel/panic.c | 1 + + kernel/printk/nbcon.c | 32 +++++++++++++++++++++++++------- + 3 files changed, 31 insertions(+), 7 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 bool nbcon_driver_try_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) +@@ -286,6 +287,10 @@ 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 +@@ -457,6 +457,7 @@ 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 +@@ -1044,6 +1044,7 @@ 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: 0 if @con was flushed up to @stop_seq Otherwise, error code on + * failure. +@@ -1062,7 +1063,8 @@ bool nbcon_legacy_emit_next_record(struc + * returned, it cannot be expected that the unfinalized record will become + * available. + */ +-static int __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq) ++static int __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); +@@ -1071,6 +1073,7 @@ static int __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 -EPERM; +@@ -1100,13 +1103,15 @@ static int __nbcon_atomic_flush_pending_ + * 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 + * + * This will stop flushing before @stop_seq if another context has ownership. + * That context is then responsible for the flushing. Likewise, if new records + * are added while this context was flushing and there is no other context + * to handle the printing, this context must also flush those records. + */ +-static void nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq) ++static void nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq, ++ bool allow_unsafe_takeover) + { + unsigned long flags; + int err; +@@ -1120,7 +1125,7 @@ static void nbcon_atomic_flush_pending_c + */ + local_irq_save(flags); + +- err = __nbcon_atomic_flush_pending_con(con, stop_seq); ++ err = __nbcon_atomic_flush_pending_con(con, stop_seq, allow_unsafe_takeover); + + local_irq_restore(flags); + +@@ -1144,8 +1149,9 @@ static void nbcon_atomic_flush_pending_c + * __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; + int cookie; +@@ -1163,7 +1169,7 @@ static void __nbcon_atomic_flush_pending + if (nbcon_seq_read(con) >= stop_seq) + continue; + +- nbcon_atomic_flush_pending_con(con, stop_seq); ++ nbcon_atomic_flush_pending_con(con, stop_seq, allow_unsafe_takeover); + } + console_srcu_read_unlock(cookie); + } +@@ -1178,7 +1184,19 @@ 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); + } + + /** +@@ -1307,7 +1325,7 @@ void nbcon_driver_release(struct console + cookie = console_srcu_read_lock(); + if (console_is_usable(con, console_srcu_read_flags(con)) && + prb_read_valid(prb, nbcon_seq_read(con), NULL)) { +- __nbcon_atomic_flush_pending_con(con, prb_next_reserve_seq(prb)); ++ __nbcon_atomic_flush_pending_con(con, prb_next_reserve_seq(prb), false); + } + console_srcu_read_unlock(cookie); + } |