[PATCH] Fix wrong irq enable via rtc_control()

rtc_control() may be called in the interrupt context in ALSA rtc-timer
driver.  The patch fixes the wrong irq enable in rtc.c, and also fixes
the possible race of bit flags.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 38 insertions, 27 deletions

diff --git a/drivers/char/rtc.c b/drivers/char/rtc.c
index 63fff7c1244a..a7f099fb7dfe 100644
--- a/drivers/char/rtc.c
+++ b/drivers/char/rtc.c
@@ -149,8 +149,22 @@ static void get_rtc_alm_time (struct rtc_time *alm_tm);
 #ifdef RTC_IRQ
 static void rtc_dropped_irq(unsigned long data);
 
-static void set_rtc_irq_bit(unsigned char bit);
-static void mask_rtc_irq_bit(unsigned char bit);
+static void set_rtc_irq_bit_locked(unsigned char bit);
+static void mask_rtc_irq_bit_locked(unsigned char bit);
+
+static inline void set_rtc_irq_bit(unsigned char bit)
+{
+        spin_lock_irq(&rtc_lock);
+        set_rtc_irq_bit_locked(bit);
+        spin_unlock_irq(&rtc_lock);
+}
+
+static void mask_rtc_irq_bit(unsigned char bit)
+{
+        spin_lock_irq(&rtc_lock);
+        mask_rtc_irq_bit_locked(bit);
+        spin_unlock_irq(&rtc_lock);
+}
 #endif
 
 static int rtc_proc_open(struct inode *inode, struct file *file);
@@ -401,18 +415,19 @@ static int rtc_do_ioctl(unsigned int cmd, unsigned long arg, int kernel)
         }
         case RTC_PIE_OFF:       /* Mask periodic int. enab. bit */
         {
-                mask_rtc_irq_bit(RTC_PIE);
+                unsigned long flags; /* can be called from isr via rtc_control() */
+                spin_lock_irqsave (&rtc_lock, flags);
+                mask_rtc_irq_bit_locked(RTC_PIE);
                 if (rtc_status & RTC_TIMER_ON) {
-                        spin_lock_irq (&rtc_lock);
                         rtc_status &= ~RTC_TIMER_ON;
                         del_timer(&rtc_irq_timer);
-                        spin_unlock_irq (&rtc_lock);
                 }
+                spin_unlock_irqrestore (&rtc_lock, flags);
                 return 0;
         }
         case RTC_PIE_ON:        /* Allow periodic ints          */
         {
-
+                unsigned long flags; /* can be called from isr via rtc_control() */
                 /*
                  * We don't really want Joe User enabling more
                  * than 64Hz of interrupts on a multi-user machine.
@@ -421,14 +436,14 @@ static int rtc_do_ioctl(unsigned int cmd, unsigned long arg, int kernel)
                         (!capable(CAP_SYS_RESOURCE)))
                         return -EACCES;
 
+                spin_lock_irqsave (&rtc_lock, flags);
                 if (!(rtc_status & RTC_TIMER_ON)) {
-                        spin_lock_irq (&rtc_lock);
                         rtc_irq_timer.expires = jiffies + HZ/rtc_freq + 2*HZ/100;
                         add_timer(&rtc_irq_timer);
                         rtc_status |= RTC_TIMER_ON;
-                        spin_unlock_irq (&rtc_lock);
                 }
-                set_rtc_irq_bit(RTC_PIE);
+                set_rtc_irq_bit_locked(RTC_PIE);
+                spin_unlock_irqrestore (&rtc_lock, flags);
                 return 0;
         }
         case RTC_UIE_OFF:       /* Mask ints from RTC updates.  */
@@ -609,6 +624,7 @@ static int rtc_do_ioctl(unsigned int cmd, unsigned long arg, int kernel)
         {
                 int tmp = 0;
                 unsigned char val;
+                unsigned long flags; /* can be called from isr via rtc_control() */
 
                 /* 
                  * The max we can do is 8192Hz.
@@ -631,9 +647,9 @@ static int rtc_do_ioctl(unsigned int cmd, unsigned long arg, int kernel)
                 if (arg != (1<<tmp))
                         return -EINVAL;
 
-                spin_lock_irq(&rtc_lock);
+                spin_lock_irqsave(&rtc_lock, flags);
                 if (hpet_set_periodic_freq(arg)) {
-                        spin_unlock_irq(&rtc_lock);
+                        spin_unlock_irqrestore(&rtc_lock, flags);
                         return 0;
                 }
                 rtc_freq = arg;
@@ -641,7 +657,7 @@ static int rtc_do_ioctl(unsigned int cmd, unsigned long arg, int kernel)
                 val = CMOS_READ(RTC_FREQ_SELECT) & 0xf0;
                 val |= (16 - tmp);
                 CMOS_WRITE(val, RTC_FREQ_SELECT);
-                spin_unlock_irq(&rtc_lock);
+                spin_unlock_irqrestore(&rtc_lock, flags);
                 return 0;
         }
 #endif
@@ -844,12 +860,15 @@ int rtc_control(rtc_task_t *task, unsigned int cmd, unsigned long arg)
 #ifndef RTC_IRQ
         return -EIO;
 #else
-        spin_lock_irq(&rtc_task_lock);
+        unsigned long flags;
+        if (cmd != RTC_PIE_ON && cmd != RTC_PIE_OFF && cmd != RTC_IRQP_SET)
+                return -EINVAL;
+        spin_lock_irqsave(&rtc_task_lock, flags);
         if (rtc_callback != task) {
-                spin_unlock_irq(&rtc_task_lock);
+                spin_unlock_irqrestore(&rtc_task_lock, flags);
                 return -ENXIO;
         }
-        spin_unlock_irq(&rtc_task_lock);
+        spin_unlock_irqrestore(&rtc_task_lock, flags);
         return rtc_do_ioctl(cmd, arg, 1);
 #endif
 }
@@ -1306,40 +1325,32 @@ static void get_rtc_alm_time(struct rtc_time *alm_tm)
  * meddles with the interrupt enable/disable bits.
  */
 
-static void mask_rtc_irq_bit(unsigned char bit)
+static void mask_rtc_irq_bit_locked(unsigned char bit)
 {
         unsigned char val;
 
-        spin_lock_irq(&rtc_lock);
-        if (hpet_mask_rtc_irq_bit(bit)) {
-                spin_unlock_irq(&rtc_lock);
+        if (hpet_mask_rtc_irq_bit(bit))
                 return;
-        }
         val = CMOS_READ(RTC_CONTROL);
         val &=  ~bit;
         CMOS_WRITE(val, RTC_CONTROL);
         CMOS_READ(RTC_INTR_FLAGS);
 
         rtc_irq_data = 0;
-        spin_unlock_irq(&rtc_lock);
 }
 
-static void set_rtc_irq_bit(unsigned char bit)
+static void set_rtc_irq_bit_locked(unsigned char bit)
 {
         unsigned char val;
 
-        spin_lock_irq(&rtc_lock);
-        if (hpet_set_rtc_irq_bit(bit)) {
-                spin_unlock_irq(&rtc_lock);
+        if (hpet_set_rtc_irq_bit(bit))
                 return;
-        }
         val = CMOS_READ(RTC_CONTROL);
         val |= bit;
         CMOS_WRITE(val, RTC_CONTROL);
         CMOS_READ(RTC_INTR_FLAGS);
 
         rtc_irq_data = 0;
-        spin_unlock_irq(&rtc_lock);
 }
 #endif