diff options
| author | Mateusz Jończyk <mat.jonczyk@o2.pl> | 2025-06-07 23:06:08 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-07-10 16:04:41 +0200 |
| commit | bd6c1932ac9c28a4a1aca2c355ebfab3d239d04f (patch) | |
| tree | 23f93a6b2b124a70477f13007d1368ca9bcb534b | |
| parent | ee61aec8529efb8b50260ce731ddaf831bc11d4a (diff) | |
rtc: cmos: use spin_lock_irqsave in cmos_interrupt
commit 00a39d8652ff9088de07a6fe6e9e1893452fe0dd upstream.
cmos_interrupt() can be called in a non-interrupt context, such as in
an ACPI event handler (which runs in an interrupt thread). Therefore,
usage of spin_lock(&rtc_lock) is insecure. Use spin_lock_irqsave() /
spin_unlock_irqrestore() instead.
Before a misguided
commit 6950d046eb6e ("rtc: cmos: Replace spin_lock_irqsave with spin_lock in hard IRQ")
the cmos_interrupt() function used spin_lock_irqsave(). That commit
changed it to spin_lock() and broke locking, which was partially fixed in
commit 13be2efc390a ("rtc: cmos: Disable irq around direct invocation of cmos_interrupt()")
That second commit did not take account of the ACPI fixed event handler
pathway, however. It introduced local_irq_disable() workarounds in
cmos_check_wkalrm(), which can cause problems on PREEMPT_RT kernels
and are now unnecessary.
Add an explicit comment so that this change will not be reverted by
mistake.
Cc: stable@vger.kernel.org
Fixes: 6950d046eb6e ("rtc: cmos: Replace spin_lock_irqsave with spin_lock in hard IRQ")
Signed-off-by: Mateusz Jończyk <mat.jonczyk@o2.pl>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Reported-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Closes: https://lore.kernel.org/all/aDtJ92foPUYmGheF@debian.local/
Link: https://lore.kernel.org/r/20250607210608.14835-1-mat.jonczyk@o2.pl
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/rtc/rtc-cmos.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c index 5849d2970bba..095de4e0e4f3 100644 --- a/drivers/rtc/rtc-cmos.c +++ b/drivers/rtc/rtc-cmos.c @@ -697,8 +697,12 @@ static irqreturn_t cmos_interrupt(int irq, void *p) { u8 irqstat; u8 rtc_control; + unsigned long flags; - spin_lock(&rtc_lock); + /* We cannot use spin_lock() here, as cmos_interrupt() is also called + * in a non-irq context. + */ + spin_lock_irqsave(&rtc_lock, flags); /* When the HPET interrupt handler calls us, the interrupt * status is passed as arg1 instead of the irq number. But @@ -732,7 +736,7 @@ static irqreturn_t cmos_interrupt(int irq, void *p) hpet_mask_rtc_irq_bit(RTC_AIE); CMOS_READ(RTC_INTR_FLAGS); } - spin_unlock(&rtc_lock); + spin_unlock_irqrestore(&rtc_lock, flags); if (is_intr(irqstat)) { rtc_update_irq(p, 1, irqstat); @@ -1300,9 +1304,7 @@ static void cmos_check_wkalrm(struct device *dev) * ACK the rtc irq here */ if (t_now >= cmos->alarm_expires && cmos_use_acpi_alarm()) { - local_irq_disable(); cmos_interrupt(0, (void *)cmos->rtc); - local_irq_enable(); return; } |