diff options
| author | Jacques Nilo <jnilo@free.fr> | 2026-05-13 15:30:23 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-05-22 11:51:35 +0200 |
| commit | c3cce2e67bb22a223f5b8ef05db0fcde70994068 (patch) | |
| tree | 2676478765d7eb0cec1f97cbb3c643e1350da7ff /include | |
| parent | a3bb136bff5e6a5e48cdd813246c9c4686feaaa9 (diff) | |
serial: core: introduce guard(uart_port_lock_check_sysrq_irqsave)
uart_handle_break() and uart_prepare_sysrq_char() (in
include/linux/serial_core.h) capture a SysRq character into
port->sysrq_ch while the port lock is held and rely on the unlock
helper -- uart_unlock_and_check_sysrq_irqrestore() -- to dispatch the
captured character to handle_sysrq() on scope exit.
The existing guard(uart_port_lock_irqsave) cannot be used by IRQ
handlers that process RX, because its destructor calls plain
uart_port_unlock_irqrestore() and silently drops port->sysrq_ch.
Add a dedicated guard(uart_port_lock_check_sysrq_irqsave) variant
whose destructor is the sysrq-aware unlock helper. The lock side is
identical to uart_port_lock_irqsave -- only the unlock-time behaviour
differs. Callers that may capture SysRq characters must use
guard(uart_port_lock_check_sysrq_irqsave); the existing
guard(uart_port_lock_irqsave) keeps its current plain-unlock semantics
for the many callers that do not process RX.
The new macro is placed after the CONFIG_MAGIC_SYSRQ_SERIAL block so
both definitions of uart_unlock_and_check_sysrq_irqrestore() (sysrq
enabled and disabled) are visible at expansion time. When
CONFIG_MAGIC_SYSRQ_SERIAL=n the destructor degenerates to plain
uart_port_unlock_irqrestore(), so there is no overhead.
No functional change on its own; users are converted in the following
patches.
Cc: stable@vger.kernel.org
Signed-off-by: Jacques Nilo <jnilo@free.fr>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://patch.msgid.link/3849af4bc55d5d2a424fa850844e94d641b2f8a6.1778675349.git.jnilo@free.fr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/serial_core.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index 666430b47899..110ad4e2aef9 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -1275,6 +1275,18 @@ static inline void uart_unlock_and_check_sysrq_irqrestore(struct uart_port *port #endif /* CONFIG_MAGIC_SYSRQ_SERIAL */ /* + * Variant of guard(uart_port_lock_irqsave) for IRQ handlers that may capture + * a SysRq character via uart_prepare_sysrq_char(). The destructor uses the + * sysrq-aware unlock helper so that a captured port->sysrq_ch is dispatched + * to handle_sysrq() on scope exit. The plain guard variant silently drops + * sysrq_ch and must not be used by callers that process RX. + */ +DEFINE_LOCK_GUARD_1(uart_port_lock_check_sysrq_irqsave, struct uart_port, + uart_port_lock_irqsave(_T->lock, &_T->flags), + uart_unlock_and_check_sysrq_irqrestore(_T->lock, _T->flags), + unsigned long flags); + +/* * We do the SysRQ and SAK checking like this... */ static inline int uart_handle_break(struct uart_port *port) |