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Merge branch 'rework/fixes' into for-linus

pull/1314/head
Petr Mladek 2025-08-04 14:18:01 +02:00
parent 8ac4bf010b 571c1ea91a
commit 3db488c8ed
1 changed files with 41 additions and 22 deletions
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63
kernel/printk/nbcon.c
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@ -214,8 +214,9 @@ static void nbcon_seq_try_update(struct nbcon_context *ctxt, u64 new_seq)
/**
* nbcon_context_try_acquire_direct - Try to acquire directly
* @ctxt: The context of the caller
* @cur: The current console state
* @ctxt: The context of the caller
* @cur: The current console state
* @is_reacquire: This acquire is a reacquire
*
* Acquire the console when it is released. Also acquire the console when
* the current owner has a lower priority and the console is in a safe state.
@ -225,17 +226,17 @@ static void nbcon_seq_try_update(struct nbcon_context *ctxt, u64 new_seq)
*
* Errors:
*
* -EPERM: A panic is in progress and this is not the panic CPU.
* Or the current owner or waiter has the same or higher
* priority. No acquire method can be successful in
* this case.
* -EPERM: A panic is in progress and this is neither the panic
* CPU nor is this a reacquire. Or the current owner or
* waiter has the same or higher priority. No acquire
* method can be successful in these cases.
*
* -EBUSY: The current owner has a lower priority but the console
* in an unsafe state. The caller should try using
* the handover acquire method.
*/
static int nbcon_context_try_acquire_direct(struct nbcon_context *ctxt,
struct nbcon_state *cur)
struct nbcon_state *cur, bool is_reacquire)
{
unsigned int cpu = smp_processor_id();
struct console *con = ctxt->console;
@ -243,14 +244,20 @@ static int nbcon_context_try_acquire_direct(struct nbcon_context *ctxt,
do {
/*
* Panic does not imply that the console is owned. However, it
* is critical that non-panic CPUs during panic are unable to
* acquire ownership in order to satisfy the assumptions of
* nbcon_waiter_matches(). In particular, the assumption that
* lower priorities are ignored during panic.
* Panic does not imply that the console is owned. However,
* since all non-panic CPUs are stopped during panic(), it
* is safer to have them avoid gaining console ownership.
*
* If this acquire is a reacquire (and an unsafe takeover
* has not previously occurred) then it is allowed to attempt
* a direct acquire in panic. This gives console drivers an
* opportunity to perform any necessary cleanup if they were
* interrupted by the panic CPU while printing.
*/
if (other_cpu_in_panic())
if (other_cpu_in_panic() &&
(!is_reacquire || cur->unsafe_takeover)) {
return -EPERM;
}
if (ctxt->prio <= cur->prio || ctxt->prio <= cur->req_prio)
return -EPERM;
@ -301,8 +308,9 @@ static bool nbcon_waiter_matches(struct nbcon_state *cur, int expected_prio)
* Event #1 implies this context is EMERGENCY.
* Event #2 implies the new context is PANIC.
* Event #3 occurs when panic() has flushed the console.
* Events #4 and #5 are not possible due to the other_cpu_in_panic()
* check in nbcon_context_try_acquire_direct().
* Event #4 occurs when a non-panic CPU reacquires.
* Event #5 is not possible due to the other_cpu_in_panic() check
* in nbcon_context_try_acquire_handover().
*/
return (cur->req_prio == expected_prio);
@ -431,6 +439,16 @@ static int nbcon_context_try_acquire_handover(struct nbcon_context *ctxt,
WARN_ON_ONCE(ctxt->prio <= cur->prio || ctxt->prio <= cur->req_prio);
WARN_ON_ONCE(!cur->unsafe);
/*
* Panic does not imply that the console is owned. However, it
* is critical that non-panic CPUs during panic are unable to
* wait for a handover in order to satisfy the assumptions of
* nbcon_waiter_matches(). In particular, the assumption that
* lower priorities are ignored during panic.
*/
if (other_cpu_in_panic())
return -EPERM;
/* Handover is not possible on the same CPU. */
if (cur->cpu == cpu)
return -EBUSY;
@ -558,7 +576,8 @@ static struct printk_buffers panic_nbcon_pbufs;
/**
* nbcon_context_try_acquire - Try to acquire nbcon console
* @ctxt: The context of the caller
* @ctxt: The context of the caller
* @is_reacquire: This acquire is a reacquire
*
* Context: Under @ctxt->con->device_lock() or local_irq_save().
* Return: True if the console was acquired. False otherwise.
@ -568,7 +587,7 @@ static struct printk_buffers panic_nbcon_pbufs;
* in an unsafe state. Otherwise, on success the caller may assume
* the console is not in an unsafe state.
*/
static bool nbcon_context_try_acquire(struct nbcon_context *ctxt)
static bool nbcon_context_try_acquire(struct nbcon_context *ctxt, bool is_reacquire)
{
unsigned int cpu = smp_processor_id();
struct console *con = ctxt->console;
@ -577,7 +596,7 @@ static bool nbcon_context_try_acquire(struct nbcon_context *ctxt)
nbcon_state_read(con, &cur);
try_again:
err = nbcon_context_try_acquire_direct(ctxt, &cur);
err = nbcon_context_try_acquire_direct(ctxt, &cur, is_reacquire);
if (err != -EBUSY)
goto out;
@ -913,7 +932,7 @@ void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt)
{
struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
while (!nbcon_context_try_acquire(ctxt))
while (!nbcon_context_try_acquire(ctxt, true))
cpu_relax();
nbcon_write_context_set_buf(wctxt, NULL, 0);
@ -1101,7 +1120,7 @@ static bool nbcon_emit_one(struct nbcon_write_context *wctxt, bool use_atomic)
cant_migrate();
}
if (!nbcon_context_try_acquire(ctxt))
if (!nbcon_context_try_acquire(ctxt, false))
goto out;
/*
@ -1486,7 +1505,7 @@ static int __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq,
ctxt->prio = nbcon_get_default_prio();
ctxt->allow_unsafe_takeover = allow_unsafe_takeover;
if (!nbcon_context_try_acquire(ctxt))
if (!nbcon_context_try_acquire(ctxt, false))
return -EPERM;
while (nbcon_seq_read(con) < stop_seq) {
@ -1784,7 +1803,7 @@ bool nbcon_device_try_acquire(struct console *con)
ctxt->console = con;
ctxt->prio = NBCON_PRIO_NORMAL;
if (!nbcon_context_try_acquire(ctxt))
if (!nbcon_context_try_acquire(ctxt, false))
return false;
if (!nbcon_context_enter_unsafe(ctxt))