diff options
| author | John Ogness <john.ogness@linutronix.de> | 2023-10-20 13:03:42 +0300 |
|---|---|---|
| committer | Andy Hu <andy.hu@starfivetech.com> | 2024-12-06 13:24:25 +0300 |
| commit | 4630550b53f53e0323f5d9fb935c4bc4d6bf245b (patch) | |
| tree | dc93aa391f83f835c9fae6eda202725dd86f8dc2 | |
| parent | c25826205aa8753844e11d2f851cf74678f6bffa (diff) | |
| download | linux-4630550b53f53e0323f5d9fb935c4bc4d6bf245b.tar.xz | |
printk: nbcon: Add unsafe flushing on panic
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>
| -rw-r--r-- | include/linux/printk.h | 5 | ||||
| -rw-r--r-- | kernel/panic.c | 1 | ||||
| -rw-r--r-- | kernel/printk/nbcon.c | 18 |
3 files changed, 22 insertions, 2 deletions
diff --git a/include/linux/printk.h b/include/linux/printk.h index 2aa57a870caf..e26dcf63efb1 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -199,6 +199,7 @@ extern asmlinkage void dump_stack(void) __cold; void printk_trigger_flush(void); extern void nbcon_acquire(struct uart_port *up); extern void nbcon_release(struct uart_port *up); +void nbcon_atomic_flush_unsafe(void); #else static inline __printf(1, 0) int vprintk(const char *s, va_list args) @@ -287,6 +288,10 @@ static inline void nbcon_release(struct uart_port *up) { } +static inline void nbcon_atomic_flush_unsafe(void) +{ +} + #endif #ifdef CONFIG_SMP diff --git a/kernel/panic.c b/kernel/panic.c index ef9f9a4e928d..219b69fbe829 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -449,6 +449,7 @@ 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) { diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index 3e999784ba5c..1c01f88d596d 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -1030,8 +1030,9 @@ bool nbcon_atomic_emit_next_record(struct console *con, bool *handover, int cook * __nbcon_atomic_flush_all - 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_all(u64 stop_seq) +static void __nbcon_atomic_flush_all(u64 stop_seq, bool allow_unsafe_takeover) { struct nbcon_write_context wctxt = { }; struct nbcon_context *ctxt = &ACCESS_PRIVATE(&wctxt, ctxt); @@ -1059,6 +1060,7 @@ static void __nbcon_atomic_flush_all(u64 stop_seq) memset(ctxt, 0, sizeof(*ctxt)); ctxt->console = con; ctxt->spinwait_max_us = 2000; + ctxt->allow_unsafe_takeover = allow_unsafe_takeover; /* * Atomic flushing does not use console driver @@ -1093,7 +1095,19 @@ static void __nbcon_atomic_flush_all(u64 stop_seq) */ void nbcon_atomic_flush_all(void) { - __nbcon_atomic_flush_all(prb_next_reserve_seq(prb)); + __nbcon_atomic_flush_all(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_all(prb_next_reserve_seq(prb), true); } /** |