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When initializing an nbcon console, have nbcon_alloc() set
@nbcon_seq to the highest possible sequence number. For all
practical purposes, this will guarantee that the console
will have nothing to print until later when @nbcon_seq is
set to the proper initial printing value.
This will be particularly important once kthread printing is
introduced because nbcon_alloc() can create/start the kthread
before the desired initial sequence number is known.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240904120536.115780-6-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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The nbcon consoles will have two callbacks to be used for
different contexts. In order to determine if an nbcon console
is usable, console_is_usable() must know if it is a context
that will need to use the optional write_atomic() callback.
Also, nbcon_emit_next_record() must know which callback it
needs to call.
Add an extra parameter @use_atomic to console_is_usable() and
nbcon_emit_next_record() to specify this.
Since so far only the write_atomic() callback exists,
@use_atomic is set to true for all call sites.
For legacy consoles, @use_atomic is not used.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240904120536.115780-5-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Ensure consoles have flushed pending records before
unregistering. The console should print up to at least its
related "console disabled" record.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240904120536.115780-4-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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A follow-up change adds pr_flush() to console unregistration.
However, with boot consoles unregistration can happen very
early if there are also regular consoles registering as well.
In this case the pr_flush() is not important because all
consoles are flushed when checking the initial console sequence
number.
Allow pr_flush() to fail if @system_state has not yet reached
SYSTEM_SCHEDULING. This avoids might_sleep() and msleep()
explosions that would otherwise occur:
[ 0.436739][ T0] printk: legacy console [ttyS0] enabled
[ 0.439820][ T0] printk: legacy bootconsole [earlyser0] disabled
[ 0.446822][ T0] BUG: scheduling while atomic: swapper/0/0/0x00000002
[ 0.450491][ T0] 1 lock held by swapper/0/0:
[ 0.457897][ T0] #0: ffffffff82ae5f88 (console_mutex){+.+.}-{4:4}, at: console_list_lock+0x20/0x70
[ 0.463141][ T0] Modules linked in:
[ 0.465307][ T0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.10.0-rc1+ #372
[ 0.469394][ T0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
[ 0.474402][ T0] Call Trace:
[ 0.476246][ T0] <TASK>
[ 0.481473][ T0] dump_stack_lvl+0x93/0xb0
[ 0.483949][ T0] dump_stack+0x10/0x20
[ 0.486256][ T0] __schedule_bug+0x68/0x90
[ 0.488753][ T0] __schedule+0xb9b/0xd80
[ 0.491179][ T0] ? lock_release+0xb5/0x270
[ 0.493732][ T0] schedule+0x43/0x170
[ 0.495998][ T0] schedule_timeout+0xc5/0x1e0
[ 0.498634][ T0] ? __pfx_process_timeout+0x10/0x10
[ 0.501522][ T0] ? msleep+0x13/0x50
[ 0.503728][ T0] msleep+0x3c/0x50
[ 0.505847][ T0] __pr_flush.constprop.0.isra.0+0x56/0x500
[ 0.509050][ T0] ? _printk+0x58/0x80
[ 0.511332][ T0] ? lock_is_held_type+0x9c/0x110
[ 0.514106][ T0] unregister_console_locked+0xe1/0x450
[ 0.517144][ T0] register_console+0x509/0x620
[ 0.519827][ T0] ? __pfx_univ8250_console_init+0x10/0x10
[ 0.523042][ T0] univ8250_console_init+0x24/0x40
[ 0.525845][ T0] console_init+0x43/0x210
[ 0.528280][ T0] start_kernel+0x493/0x980
[ 0.530773][ T0] x86_64_start_reservations+0x18/0x30
[ 0.533755][ T0] x86_64_start_kernel+0xae/0xc0
[ 0.536473][ T0] common_startup_64+0x12c/0x138
[ 0.539210][ T0] </TASK>
And then the kernel goes into an infinite loop complaining about:
1. releasing a pinned lock
2. unpinning an unpinned lock
3. bad: scheduling from the idle thread!
4. goto 1
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240904120536.115780-3-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Since ownership can be lost at any time due to handover or
takeover, a printing context _must_ be prepared to back out
immediately and carefully. However, there are scenarios where
the printing context must reacquire ownership in order to
finalize or revert hardware changes.
One such example is when interrupts are disabled during
printing. No other context will automagically re-enable the
interrupts. For this case, the disabling context _must_
reacquire nbcon ownership so that it can re-enable the
interrupts.
Provide nbcon_reacquire_nobuf() for exactly this purpose. It
allows a printing context to reacquire ownership using the same
priority as its previous ownership.
Note that after a successful reacquire the printing context
will have no output buffer because that has been lost. This
function cannot be used to resume printing.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240904120536.115780-2-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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There is no need to open code a non-migration-checking
this_cpu_ptr(). That is exactly what raw_cpu_ptr() is.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/87plpum4jw.fsf@jogness.linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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sizeof(unsigned long) * 8 is the number of bits in an unsigned long
variable, replace it with BITS_PER_LONG macro to make it simpler.
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240903035358.308482-1-ruanjinjie@huawei.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Mark emergency sections wherever multiple lines of
lock debugging output are generated. In an emergency
section, every printk() call will attempt to directly
flush to the consoles using the EMERGENCY priority.
Note that debug_show_all_locks() and
lockdep_print_held_locks() rely on their callers to
enter the emergency section. This is because these
functions can also be called in non-emergency
situations (such as sysrq).
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-36-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Mark emergency sections wherever multiple lines of
rcu stall information are generated. In an emergency
section, every printk() call will attempt to directly
flush to the consoles using the EMERGENCY priority.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20240820063001.36405-35-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Mark an emergency section beginning with oops_enter() until the
end of oops_exit(). In this section, every printk() call will
attempt to directly flush to the consoles using the EMERGENCY
priority.
The very end of oops_exit() performs a kmsg_dump(). This is not
included in the emergency section because it is another
flushing mechanism that should occur after the consoles have
flushed the oops messages.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-34-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Mark the full contents of __warn() as an emergency section. In
this section, every printk() call will attempt to directly
flush to the consoles using the EMERGENCY priority.
Co-developed-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-33-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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In emergency situations (something has gone wrong but the
system continues to operate), usually important information
(such as a backtrace) is generated via printk(). This
information should be pushed out to the consoles ASAP.
Add per-CPU emergency nesting tracking because an emergency
can arise while in an emergency situation.
Add functions to mark the beginning and end of emergency
sections where the urgent messages are generated.
Perform direct console flushing at the emergency priority if
the current CPU is in an emergency state and it is safe to do
so.
Note that the emergency state is not system-wide. While one CPU
is in an emergency state, another CPU may attempt to print
console messages at normal priority.
Also note that printk() already attempts to flush consoles in
the caller context for normal priority. However, follow-up
changes will introduce printing kthreads, in which case the
normal priority printk() calls will offload to the kthreads.
Co-developed-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-32-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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There are many call sites where console flushing occur.
Depending on the system state and types of consoles, the flush
methods to use are different. A flush call site generally must
consider:
@have_boot_console
@have_nbcon_console
@have_legacy_console
@legacy_allow_panic_sync
is_printk_preferred()
and take into account the current CPU state:
NBCON_PRIO_NORMAL
NBCON_PRIO_EMERGENCY
NBCON_PRIO_PANIC
in order to decide if it should:
flush nbcon directly via atomic_write() callback
flush legacy directly via console_unlock
flush legacy via offload to irq_work
All of these call sites use their own logic to make this
decision, which is complicated and error prone. Especially
later when two more flush methods will be introduced:
flush nbcon via offload to kthread
flush legacy via offload to kthread
Introduce a new internal struct console_flush_type that specifies
which console flushing methods should be used in the context of
the caller.
Introduce a helper function to fill out console_flush_type to
be used for flushing call sites.
Replace the logic of all flushing call sites to use the new
helper.
This change standardizes behavior, leading to both fixes and
optimizations across various call sites. For instance, in
console_cpu_notify(), the new logic ensures that nbcon consoles
are flushed when they aren’t managed by the legacy loop.
Similarly, in console_flush_on_panic(), the system no longer
needs to flush nbcon consoles if none are present.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-31-john.ogness@linutronix.de
[pmladek@suse.com: Updated the commit message.]
Signed-off-by: Petr Mladek <pmladek@suse.com>
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If legacy and nbcon consoles are registered and the nbcon
consoles are allowed to flush (i.e. no boot consoles
registered), the legacy consoles will no longer perform
direct printing on the panic CPU until after the backtrace
has been stored. This will give the safe nbcon consoles a
chance to print the panic messages before allowing the
unsafe legacy consoles to print.
If no nbcon consoles are registered or they are not allowed
to flush because boot consoles are registered, there is no
change in behavior (i.e. legacy consoles will always attempt
to print from the printk() caller context).
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-30-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Add a global flag @have_nbcon_console to identify if any nbcon
consoles are registered. This will be used in follow-up commits
to preserve legacy behavior when no nbcon consoles are registered.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-29-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Currently the console lock is used to attempt legacy-type
printing even if there are no legacy or boot consoles registered.
If no such consoles are registered, the console lock does not
need to be taken.
Add tracking of legacy console registration and use it with
boot console tracking to avoid unnecessary code paths, i.e.
do not use the console lock if there are no boot consoles
and no legacy consoles.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-28-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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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>
Link: https://lore.kernel.org/r/20240820063001.36405-27-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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In console_flush_on_panic(), flush the nbcon consoles before
flushing legacy consoles. The legacy write() callbacks are not
fully safe when oops_in_progress is set.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-26-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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There may be new records that were added while a driver was
holding the nbcon context for non-printing purposes. These
new records must be flushed by the nbcon_device_release()
context because no other context will do it.
If boot consoles are registered, the legacy loop is used
(either direct or per irq_work) to handle the flushing.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-25-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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If printk has been explicitly deferred or is called from NMI
context, legacy console printing must be deferred to an irq_work
context. Introduce a helper function is_printk_legacy_deferred()
for a CPU to query if it must defer legacy console printing.
In follow-up commits this helper will be needed at other call
sites as well.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-24-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Allow nbcon consoles to print messages in the legacy printk()
caller context (printing via unlock) by integrating them into
console_flush_all(). The write_atomic() callback is used for
printing.
Provide nbcon_legacy_emit_next_record(), which acts as the
nbcon variant of console_emit_next_record(). Call this variant
within console_flush_all() for nbcon consoles. Since nbcon
consoles use their own @nbcon_seq variable to track the next
record to print, this also must be appropriately handled in
console_flush_all().
Note that the legacy printing logic uses @handover to detect
handovers for printing all consoles. For nbcon consoles,
handovers/takeovers occur on a per-console basis and thus do
not cause the console_flush_all() loop to abort.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-23-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Unfortunately it is not known if a boot console and a regular
(legacy or nbcon) console use the same hardware. For this reason
they must not be allowed to print simultaneously.
For legacy consoles this is not an issue because they are
already synchronized with the boot consoles using the console
lock. However nbcon consoles can be triggered separately.
Add a global flag @have_boot_console to identify if any boot
consoles are registered. This will be used in follow-up commits
to ensure that boot consoles and nbcon consoles cannot print
simultaneously.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-22-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Provide nbcon_atomic_flush_pending() to perform flushing of all
registered nbcon consoles using their write_atomic() callback.
Unlike console_flush_all(), nbcon_atomic_flush_pending() will
only flush up through the newest record at the time of the
call. This prevents a CPU from printing unbounded when other
CPUs are adding records. If new records are added while
flushing, it is expected that the dedicated printer threads
will print those records. If the printer thread is not
available (which is always the case at this point in the
rework), nbcon_atomic_flush_pending() _will_ flush all records
in the ringbuffer.
Unlike console_flush_all(), nbcon_atomic_flush_pending() will
fully flush one console before flushing the next. This helps to
guarantee that a block of pending records (such as a stack
trace in an emergency situation) can be printed atomically at
once before releasing console ownership.
nbcon_atomic_flush_pending() is safe in any context because it
uses write_atomic() and acquires with unsafe_takeover disabled.
Co-developed-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-21-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Add a helper function to use the current state of the CPU to
determine which priority to assign to the printing context.
The EMERGENCY priority handling is added in a follow-up commit.
It will use a per-CPU variable.
Note: nbcon_device_try_acquire(), which is used by console
drivers to acquire the nbcon console for non-printing
activities, is hard-coded to always use NORMAL priority.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-20-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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The caller of console_is_usable() usually needs @console->flags
for its own checks. Rather than having console_is_usable() read
its own copy, make the caller pass in the @flags. This also
ensures that the caller saw the same @flags value.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-19-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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The nbcon consoles use a different printing callback. For nbcon
consoles, check for the write_atomic() callback instead of
write().
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-18-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Move console_is_usable() as-is into internal.h so that it can
be used by nbcon printing functions as well.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-17-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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The headers kernel.h, serial_core.h, and console.h allow for the
definitions of many types and functions from other headers.
Rather than relying on these as proxy headers, explicitly
include all headers providing needed definitions. Also sort the
list alphabetically to be able to easily detect duplicates.
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-16-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Currently the port->lock wrappers uart_port_lock(),
uart_port_unlock() (and their variants) only lock/unlock
the spin_lock.
If the port is an nbcon console that has implemented the
write_atomic() callback, the wrappers must also acquire/release
the console context and mark the region as unsafe. This allows
general port->lock synchronization to be synchronized against
the nbcon write_atomic() callback.
Note that __uart_port_using_nbcon() relies on the port->lock
being held while a console is added and removed from the
console list (i.e. all uart nbcon drivers *must* take the
port->lock in their device_lock() callbacks).
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-15-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Provide functions nbcon_device_try_acquire() and
nbcon_device_release() which will try to acquire the nbcon
console ownership with NBCON_PRIO_NORMAL and mark it unsafe for
handover/takeover.
These functions are to be used together with the device-specific
locking when performing non-printing activities on the console
device. They will allow synchronization against the
atomic_write() callback which will be serialized, for higher
priority contexts, only by acquiring the console context
ownership.
Pitfalls:
The API requires to be called in a context with migration
disabled because it uses per-CPU variables internally.
The context is set unsafe for a takeover all the time. It
guarantees full serialization against any atomic_write() caller
except for the final flush in panic() which might try an unsafe
takeover.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-14-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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It was not clear when exactly console_srcu_read_flags() must be
used vs. directly reading @console->flags.
Refactor and clarify that console_srcu_read_flags() is only
needed if the console is registered or the caller is in a
context where the registration status of the console may change
(due to another context).
The function requires the caller holds @console_srcu, which will
ensure that the caller sees an appropriate @flags value for the
registered console and that exit/cleanup routines will not run
if the console is in the process of unregistration.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-13-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Introduce uart_port_set_cons() as a wrapper to set @cons of a
uart_port. The wrapper sets @cons under the port lock in order
to prevent @cons from disappearing while another context is
holding the port lock. This is necessary for a follow-up
commit relating to the port lock wrappers, which rely on @cons
not changing between lock and unlock.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Tested-by: Théo Lebrun <theo.lebrun@bootlin.com> # EyeQ5, AMBA-PL011
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240820063001.36405-12-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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It will be necessary at times for the uart nbcon console
drivers to acquire the port lock directly (without the
additional nbcon functionality of the port lock wrappers).
These are special cases such as the implementation of the
device_lock()/device_unlock() callbacks or for internal
port lock wrapper synchronization.
Provide low-level variants __uart_port_lock_irqsave() and
__uart_port_unlock_irqrestore() for this purpose.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20240820063001.36405-11-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Console drivers typically have to deal with access to the
hardware via user input/output (such as an interactive login
shell) and output of kernel messages via printk() calls.
They use some classic driver-specific locking mechanism in most
situations. But console->write_atomic() callbacks, used by nbcon
consoles, are synchronized only by acquiring the console
context.
The synchronization via the console context ownership is possible
only when the console driver is registered. It is when a
particular device driver is connected with a particular console
driver.
The two synchronization mechanisms must be synchronized between
each other. It is tricky because the console context ownership
is quite special. It might be taken over by a higher priority
context. Also CPU migration must be disabled. The most tricky
part is to (dis)connect these two mechanisms during the console
(un)registration.
Use the driver-specific locking callbacks: device_lock(),
device_unlock(). They allow taking the device-specific lock
while the device is being (un)registered by the related console
driver.
For example, these callbacks lock/unlock the port lock for
serial port drivers.
Note that the driver-specific locking is only needed during
(un)register if it is an nbcon console with the write_atomic()
callback implemented. If write_atomic() is not implemented, the
driver should never attempt to access the hardware without
first acquiring its driver-specific lock.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-10-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Console drivers typically must deal with access to the hardware
via user input/output (such as an interactive login shell) and
output of kernel messages via printk() calls. To provide the
necessary synchronization, usually some driver-specific locking
mechanism is used (for example, the port spinlock for uart
serial consoles).
Until now, usage of this driver-specific locking has been hidden
from the printk-subsystem and implemented within the various
console callbacks. However, nbcon consoles would need to use it
even in the generic code.
Add device_lock() and device_unlock() callback which will need
to get implemented by nbcon consoles.
The callbacks will use whatever synchronization mechanism the
driver is using for itself. The minimum requirement is to
prevent CPU migration. It would allow a context friendly
acquiring of nbcon console ownership in non-emergency and
non-panic context.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-9-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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The write_atomic() callback has special requirements and is
allowed to use special helper functions. Provide detailed
documentation of the callback so that a developer has a
chance of implementing it correctly.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-8-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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The return value of write_atomic() does not provide any useful
information. On the contrary, it makes things more complicated
for the caller to appropriately deal with the information.
Change write_atomic() to not have a return value. If the
message did not get printed due to loss of ownership, the
caller will notice this on its own. If ownership was not lost,
it will be assumed that the driver successfully printed the
message and the sequence number for that console will be
incremented.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-7-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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The functions nbcon_owner_matches() and nbcon_waiter_matches()
use a minimal set of data to determine if a context matches.
The existing kerneldoc and comments were not clear enough and
caused the printk folks to re-prove that the functions are
indeed reliable in all cases.
Update and expand the explanations so that it is clear that the
implementations are sufficient for all cases.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-6-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Add validation that printk_deferred_enter()/_exit() are called in
non-migration contexts.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-5-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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If a non-boot console is registering and boot consoles exist,
the consoles are flushed before being unregistered. This allows
the non-boot console to continue where the boot console left
off.
If for whatever reason flushing fails, the lowest seq found from
any of the enabled boot consoles is used. Until now con->seq was
checked. However, if it is an nbcon boot console, the function
nbcon_seq_read() must be used to read seq because con->seq is
not updated for nbcon consoles.
Check if it is an nbcon boot console and if so call
nbcon_seq_read() to read seq.
Also, avoid usage of con->seq as temporary storage of the
starting record. Instead, rename console_init_seq() to
get_init_console_seq() and just return the value. For nbcon
consoles set the sequence via nbcon_seq_force(), for legacy
consoles set con->seq.
The cleaned design should make sure that the value stays and is
set before the console is added to the console list. It also
unifies the sequence number initialization for legacy and nbcon
consoles.
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Link: https://lore.kernel.org/r/20240820063001.36405-4-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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Rather than splitting the nbcon allocation and initialization into
two pieces, perform all initialization in nbcon_alloc(). Later,
the initial sequence is calculated and can be explicitly set using
nbcon_seq_force(). This removes the need for the strong rules of
nbcon_init() that even included a BUG_ON().
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-3-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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kernel/printk/printk.c:284:5: sparse: sparse: context imbalance in
'console_srcu_read_lock' - wrong count at exit
include/linux/srcu.h:301:9: sparse: sparse: context imbalance in
'console_srcu_read_unlock' - unexpected unlock
Fixes: 6c4afa79147e ("printk: Prepare for SRCU console list protection")
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20240820063001.36405-2-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk fix from Petr Mladek:
- Do not block printk on non-panic CPUs when they are dumping
backtraces
* tag 'printk-for-6.11-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
printk/panic: Allow cpu backtraces to be written into ringbuffer during panic
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git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core
Pull driver core fixes from Greg KH:
"Here are two driver fixes for regressions from 6.11-rc1 due to the
driver core change making a structure in a driver core callback const.
These were missed by all testing EXCEPT for what Bart happened to be
running, so I appreciate the fixes provided here for some
odd/not-often-used driver subsystems that nothing else happened to
catch.
Both of these fixes have been in linux-next all week with no reported
issues"
* tag 'driver-core-6.11-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
mips: sgi-ip22: Fix the build
ARM: riscpc: ecard: Fix the build
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git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc
Pull char / misc fixes from Greg KH:
"Here are some small char/misc fixes for 6.11-rc4 to resolve reported
problems. Included in here are:
- fastrpc revert of a change that broke userspace
- xillybus fixes for reported issues
Half of these have been in linux-next this week with no reported
problems, I don't know if the last bit of xillybus driver changes made
it in, but they are 'obviously correct' so will be safe :)"
* tag 'char-misc-6.11-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
char: xillybus: Check USB endpoints when probing device
char: xillybus: Refine workqueue handling
Revert "misc: fastrpc: Restrict untrusted app to attach to privileged PD"
char: xillybus: Don't destroy workqueue from work item running on it
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git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty
Pull tty / serial fixes from Greg KH:
"Here are some small tty and serial driver fixes for 6.11-rc4 to
resolve some reported problems. Included in here are:
- conmakehash.c userspace build issues
- fsl_lpuart driver fix
- 8250_omap revert for reported regression
- atmel_serial rts flag fix
All of these have been in linux-next this week with no reported
issues"
* tag 'tty-6.11-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
Revert "serial: 8250_omap: Set the console genpd always on if no console suspend"
tty: atmel_serial: use the correct RTS flag.
tty: vt: conmakehash: remove non-portable code printing comment header
tty: serial: fsl_lpuart: mark last busy before uart_add_one_port
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git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb
Pull USB / Thunderbolt driver fixes from Greg KH:
"Here are some small USB and Thunderbolt driver fixes for 6.11-rc4 to
resolve some reported issues. Included in here are:
- thunderbolt driver fixes for reported problems
- typec driver fixes
- xhci fixes
- new device id for ljca usb driver
All of these have been in linux-next this week with no reported
issues"
* tag 'usb-6.11-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
xhci: Fix Panther point NULL pointer deref at full-speed re-enumeration
usb: misc: ljca: Add Lunar Lake ljca GPIO HID to ljca_gpio_hids[]
Revert "usb: typec: tcpm: clear pd_event queue in PORT_RESET"
usb: typec: ucsi: Fix the return value of ucsi_run_command()
usb: xhci: fix duplicate stall handling in handle_tx_event()
usb: xhci: Check for xhci->interrupters being allocated in xhci_mem_clearup()
thunderbolt: Mark XDomain as unplugged when router is removed
thunderbolt: Fix memory leaks in {port|retimer}_sb_regs_write()
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git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
Pull more btrfs fixes from David Sterba:
"A more fixes. We got reports that shrinker added in 6.10 still causes
latency spikes and the fixes don't handle all corner cases. Due to
summer holidays we're taking a shortcut to disable it for release
builds and will fix it in the near future.
- only enable extent map shrinker for DEBUG builds, temporary quick
fix to avoid latency spikes for regular builds
- update target inode's ctime on unlink, mandated by POSIX
- properly take lock to read/update block group's zoned variables
- add counted_by() annotations"
* tag 'for-6.11-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
btrfs: only enable extent map shrinker for DEBUG builds
btrfs: zoned: properly take lock to read/update block group's zoned variables
btrfs: tree-checker: add dev extent item checks
btrfs: update target inode's ctime on unlink
btrfs: send: annotate struct name_cache_entry with __counted_by()
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fuse_notify_store(), unlike fuse_do_readpage(), does not enable page
zeroing (because it can be used to change partial page contents).
So fuse_notify_store() must be more careful to fully initialize page
contents (including parts of the page that are beyond end-of-file)
before marking the page uptodate.
The current code can leave beyond-EOF page contents uninitialized, which
makes these uninitialized page contents visible to userspace via mmap().
This is an information leak, but only affects systems which do not
enable init-on-alloc (via CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y or the
corresponding kernel command line parameter).
Link: https://bugs.chromium.org/p/project-zero/issues/detail?id=2574
Cc: stable@kernel.org
Fixes: a1d75f258230 ("fuse: add store request")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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