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Subject[PATCH 2/2] include/delay.h: replace msleep() and msleep_interruptible() with macros
On Fri, Nov 19, 2004 at 05:23:32PM -0800, Nishanth Aravamudan wrote:
> On Fri, Nov 19, 2004 at 04:56:01PM -0800, Nishanth Aravamudan wrote:
> > On Fri, Nov 19, 2004 at 04:48:41PM -0800, Nishanth Aravamudan wrote:
> > > On Tue, Nov 16, 2004 at 06:49:44PM -0800, Nishanth Aravamudan wrote:
> > > > Hi,
> > > >
> > > > After some pretty heavy discussion on IRC, I felt that it may be
> > > > important / useful to bring the discussion of schedule_timeout() to
> > > > LKML. There are two issues being considered:
> > > >
> > > > 1) msleep_interruptible()
> > > >
> > > > For reference, here is the code for this function:
> > > >
> > > > /**
> > > > * msleep_interruptible - sleep waiting for waitqueue interruptions
> > > > * @msecs: Time in milliseconds to sleep for
> > > > */
> > > > unsigned long msleep_interruptible(unsigned int msecs)
> > > > {
> > > > unsigned long timeout = msecs_to_jiffies(msecs);
> > > >
> > > > while (timeout && !signal_pending(current)) {
> > > > set_current_state(TASK_INTERRUPTIBLE);
> > > > timeout = schedule_timeout(timeout);
> > > > }
> > > > return jiffies_to_msecs(timeout);
> > > > }
> > > >
> > > > The first issue deals with whether the while() loop is at all necessary.
> > > > From my understanding (primarily from how the code "should" behave, but
> > > > also backed up by code itself), I think the following code:
> > > >
> > > > set_current_state(TASK_INTERRUPTIBLE);
> > > > timeout = schedule_timeout(timeout);
> > > >
> > > > should be interpreted as:
> > > >
> > > > a) I wish to sleep for timeout jiffies; however
> > > > b) If a signal occurs before timeout jiffies have gone by, I
> > > > would also like to wake up.
> > > >
> > > > With this interpretation, though, the while()-conditional becomes
> > > > questionable. I can see two cases (think inclusive OR not exclusive) for
> > > > schedule_timeout() returning:
> > > >
> > > > a) A signal was received and thus signal_pending(current) will
> > > > be true, exiting the loop. In this case, timeout will be
> > > > some non-negative value (0 is a corner case, I believe, where
> > > > both the timer fires and a signal is received in the last jiffy).
> > > > b) The timer in schedule_timeout() has expired and thus it will
> > > > return 0. This indicates the function has delayed the requested
> > > > time (at least) and timeout will be set to 0, again exiting the
> > > > loop.
> > > >
> > > > Clearly, then, if my interpretion is correct, schedule_timeout() will
> > > > always return to a state in msleep_interruptible() which causes the loop
> > > > to only iterate the one time. Does this make sense? Is my interpretation
> > > > of schedule_timeout()s functioning somehow flawed? If not, we probably
> > > > can go ahead and change the msleep_interruptible() code, yes?
> > >
> > > Ok, since nobody seems to have objected to my ideas as of yet, I went
> > > ahead and implemented them, with much help from Domen and others. I
> > > believe there are two options for these changes. One involves using
> > > macros instead, the other involves reworking the functions.
> >
> > Here is patch 2/2, which modifies include/linux/delay.h to contain the
> > appropriate macros. Much consideration was given the various names and
> > calling syntax, but corrections/requests/changes are welcome.
> >
> > -Nish
> >
> > Description: Remove prototypes of msleep() and msleep_interruptible() to
> > prepare for the macro versions of these functions. Add macros for 4
> > types of sleeps:
> > 1) Unconditional sleep (msleep)
> > 2) Sleep until signalled (msleep_interruptible)
> > 3) Sleep until wait-queue event (msleep_wq)
> > 4) Sleep until either signalled or wait-queue event
> > (msleep_wq_interruptible)
> > These 4 cases are all distinct and handled separately by passing
> > appropriate flags to __msleep_sig and __msleep_wq, which should *not*
> > ever be called directly by kernel code.
> >
> > Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
> >
> > --- 2.6.10-rc2-vanilla/include/linux/delay.h 2004-11-19 16:11:52.000000000 -0800
> > +++ 2.6.10-rc2/include/linux/delay.h 2004-11-19 16:52:40.000000000 -0800
> > @@ -38,8 +38,56 @@ extern unsigned long loops_per_jiffy;
> > #define ndelay(x) udelay(((x)+999)/1000)
> > #endif
> >
> > -void msleep(unsigned int msecs);
> > -unsigned long msleep_interruptible(unsigned int msecs);
> > +/*
> > + * Sleep in state while condition is true
> > + */
> > +#define __msleep_sig(unsigned int msecs, long state, int condition) \
> > + do { \
> > + unsigned long timeout = msecs_to_jiffies(msecs) + 1; \
> > + \
> > + while (timeout && condition) { \
> > + set_current_state(state); \
> > + timeout = schedule_timeout(timeout); \
> > + } \
> > + \
> > + return jiffies_to_msecs(timeout); \
> > + } while(0)
> > +
> > +/*
> > + * Sleep in state until schedule_timeout() returns
> > + */
> > +#define __msleep_wq(unsigned int msecs, long state) \
> > + do { \
> > + unsigned long timeout = msecs_to_jiffies(msecs) + 1; \
> > + \
> > + set_current_state(condition); \
>
> Obvious typo, fixed in patch below...
>
>
> Description: Remove prototypes of msleep() and msleep_interruptible() to
> prepare for the macro versions of these functions. Add macros for 4
> types of sleeps:
> 1) Unconditional sleep (msleep)
> 2) Sleep until signalled (msleep_interruptible)
> 3) Sleep until wait-queue event (msleep_wq)
> 4) Sleep until either signalled or wait-queue event
> (msleep_wq_interruptible)
> These 4 cases are all distinct and handled separately by passing
> appropriate flags to __msleep_sig and __msleep_wq, which should *not*
> ever be called directly by kernel code.
>
> Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
>
>
> --- 2.6.10-rc2-vanilla/include/linux/delay.h 2004-11-19 16:11:52.000000000 -0800
> +++ 2.6.10-rc2/include/linux/delay.h 2004-11-19 16:52:40.000000000 -0800
> @@ -38,8 +38,56 @@ extern unsigned long loops_per_jiffy;
> #define ndelay(x) udelay(((x)+999)/1000)
> #endif
>
> -void msleep(unsigned int msecs);
> -unsigned long msleep_interruptible(unsigned int msecs);
> +/*
> + * Sleep in state while condition is true
> + */
> +#define __msleep_sig(unsigned int msecs, long state, int condition) \
> + do { \
> + unsigned long timeout = msecs_to_jiffies(msecs) + 1; \
> + \
> + while (timeout && condition) { \
> + set_current_state(state); \
> + timeout = schedule_timeout(timeout); \
> + } \
> + \
> + return jiffies_to_msecs(timeout); \
> + } while(0)
> +
> +/*
> + * Sleep in state until schedule_timeout() returns
> + */
> +#define __msleep_wq(unsigned int msecs, long state) \
> + do { \
> + unsigned long timeout = msecs_to_jiffies(msecs) + 1; \
> + \
> + set_current_state(state); \
> + timeout = schedule_timeout(timeout); \
> + \
> + return jiffies_to_msecs(timeout); \
> + } while(0)
> +
> +/*
> + * Sleep until at least msecs ms have elapsed
> + */
> +#define msleep(msecs) (void)__msleep_sig(msecs, TASK_UNINTERRUPTIBLE, 1)
> +
> +/*
> + * Sleep until at least msecs ms have elapsed or a signal is received
> + */
> +#define msleep_interruptible(msecs) \
> + __msleep_sig(msecs, TASK_INTERRUPTIBLE, !signals_pending(current))
> +
> +/*
> + * Sleep until at least msecs ms have elapsed or a wait-queue event occurs
> + */
> +#define msleep_wq(msecs) __msleep_wq_state(msecs, TASK_UNINTERRUPTIBLE)
> +
> +/*
> + * Sleep until at least msecs ms have elapsed or a wait-queue event occurs
> + * or a signal is received
> + */
> +#define msleep_wq_interruptible(msecs) \
> + __msleep_wq_state(msecs, TASK_INTERRUPTIBLE);

Another stupid typo.

Description: Remove prototypes of msleep() and msleep_interruptible() to
prepare for the macro versions of these functions. Add macros for 4
types of sleeps:
1) Unconditional sleep (msleep)
2) Sleep until signalled (msleep_interruptible)
3) Sleep until wait-queue event (msleep_wq)
4) Sleep until either signalled or wait-queue event
(msleep_wq_interruptible)
These 4 cases are all distinct and handled separately by passing
appropriate flags to __msleep_sig and __msleep_wq, which should *not*
ever be called directly by kernel code.

Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>


--- 2.6.10-rc2-vanilla/include/linux/delay.h 2004-11-19 16:11:52.000000000 -0800
+++ 2.6.10-rc2/include/linux/delay.h 2004-11-19 16:52:40.000000000 -0800
@@ -38,8 +38,56 @@ extern unsigned long loops_per_jiffy;
#define ndelay(x) udelay(((x)+999)/1000)
#endif

-void msleep(unsigned int msecs);
-unsigned long msleep_interruptible(unsigned int msecs);
+/*
+ * Sleep in state while condition is true
+ */
+#define __msleep_sig(unsigned int msecs, long state, int condition) \
+ do { \
+ unsigned long timeout = msecs_to_jiffies(msecs) + 1; \
+ \
+ while (timeout && condition) { \
+ set_current_state(state); \
+ timeout = schedule_timeout(timeout); \
+ } \
+ \
+ return jiffies_to_msecs(timeout); \
+ } while(0)
+
+/*
+ * Sleep in state until schedule_timeout() returns
+ */
+#define __msleep_wq(unsigned int msecs, long state) \
+ do { \
+ unsigned long timeout = msecs_to_jiffies(msecs) + 1; \
+ \
+ set_current_state(condition); \
+ timeout = schedule_timeout(timeout); \
+ \
+ return jiffies_to_msecs(timeout); \
+ } while(0)
+
+/*
+ * Sleep until at least msecs ms have elapsed
+ */
+#define msleep(msecs) (void)__msleep_sig(msecs, TASK_UNINTERRUPTIBLE, 1)
+
+/*
+ * Sleep until at least msecs ms have elapsed or a signal is received
+ */
+#define msleep_interruptible(msecs) \
+ __msleep_sig(msecs, TASK_INTERRUPTIBLE, !signals_pending(current))
+
+/*
+ * Sleep until at least msecs ms have elapsed or a wait-queue event occurs
+ */
+#define msleep_wq(msecs) __msleep_wq_state(msecs, TASK_UNINTERRUPTIBLE)
+
+/*
+ * Sleep until at least msecs ms have elapsed or a wait-queue event occurs
+ * or a signal is received
+ */
+#define msleep_wq_interruptible(msecs) \
+ __msleep_wq_state(msecs, TASK_INTERRUPTIBLE)

static inline void ssleep(unsigned int seconds)
{
-
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