From a0f7d48bfb95a4c5172a2756dbc4b82afc8e9ae4 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Fri, 14 Aug 2009 15:47:19 +0200 Subject: timekeeping: Remove clocksource inline functions The three inline functions clocksource_read, clocksource_enable and clocksource_disable are simple wrappers of an indirect call plus the copy from and to the mult_orig value. The functions are exclusively used by the timekeeping code which has intimate knowledge of the clocksource anyway. Therefore remove the inline functions. No functional change. Signed-off-by: Martin Schwidefsky Acked-by: John Stultz Cc: Daniel Walker LKML-Reference: <20090814134807.903108946@de.ibm.com> Signed-off-by: Thomas Gleixner --- include/linux/clocksource.h | 58 --------------------------------------------- 1 file changed, 58 deletions(-) (limited to 'include/linux/clocksource.h') diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index 1219be4fb42..a1ef46f61c8 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -267,64 +267,6 @@ static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant) return (u32)tmp; } -/** - * clocksource_read: - Access the clocksource's current cycle value - * @cs: pointer to clocksource being read - * - * Uses the clocksource to return the current cycle_t value - */ -static inline cycle_t clocksource_read(struct clocksource *cs) -{ - return cs->read(cs); -} - -/** - * clocksource_enable: - enable clocksource - * @cs: pointer to clocksource - * - * Enables the specified clocksource. The clocksource callback - * function should start up the hardware and setup mult and field - * members of struct clocksource to reflect hardware capabilities. - */ -static inline int clocksource_enable(struct clocksource *cs) -{ - int ret = 0; - - if (cs->enable) - ret = cs->enable(cs); - - /* - * The frequency may have changed while the clocksource - * was disabled. If so the code in ->enable() must update - * the mult value to reflect the new frequency. Make sure - * mult_orig follows this change. - */ - cs->mult_orig = cs->mult; - - return ret; -} - -/** - * clocksource_disable: - disable clocksource - * @cs: pointer to clocksource - * - * Disables the specified clocksource. The clocksource callback - * function should power down the now unused hardware block to - * save power. - */ -static inline void clocksource_disable(struct clocksource *cs) -{ - /* - * Save mult_orig in mult so clocksource_enable() can - * restore the value regardless if ->enable() updates - * the value of mult or not. - */ - cs->mult = cs->mult_orig; - - if (cs->disable) - cs->disable(cs); -} - /** * cyc2ns - converts clocksource cycles to nanoseconds * @cs: Pointer to clocksource -- cgit v1.2.3 From f1b82746c1e93daf24e1ab9bfbd39bcdb2e7018b Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Fri, 14 Aug 2009 15:47:21 +0200 Subject: clocksource: Cleanup clocksource selection If a non high-resolution clocksource is first set as override clock and then registered it becomes active even if the system is in one-shot mode. Move the override check from sysfs_override_clocksource to the clocksource selection. That fixes the bug and simplifies the code. The check in clocksource_register for double registration of the same clocksource is removed without replacement. To find the initial clocksource a new weak function in jiffies.c is defined that returns the jiffies clocksource. The architecture code can then override the weak function with a more suitable clocksource, e.g. the TOD clock on s390. [ tglx: Folded in a fix from John Stultz ] Signed-off-by: Martin Schwidefsky Acked-by: John Stultz Cc: Daniel Walker LKML-Reference: <20090814134808.388024160@de.ibm.com> Signed-off-by: Thomas Gleixner --- include/linux/clocksource.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/clocksource.h') diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index a1ef46f61c8..f263b3abf46 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -14,6 +14,7 @@ #include #include #include +#include #include #include @@ -322,6 +323,7 @@ extern void clocksource_touch_watchdog(void); extern struct clocksource* clocksource_get_next(void); extern void clocksource_change_rating(struct clocksource *cs, int rating); extern void clocksource_resume(void); +extern struct clocksource * __init __weak clocksource_default_clock(void); #ifdef CONFIG_GENERIC_TIME_VSYSCALL extern void update_vsyscall(struct timespec *ts, struct clocksource *c); -- cgit v1.2.3 From c55c87c892c1875deace0c8fc28787335277fdf2 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Fri, 14 Aug 2009 15:47:25 +0200 Subject: clocksource: Move watchdog downgrade to a work queue thread Move the downgrade of an unstable clocksource from the timer interrupt context into the process context of a work queue thread. This is needed to be able to do the clocksource switch with stop_machine. Signed-off-by: Martin Schwidefsky Cc: Ingo Molnar Acked-by: John Stultz Cc: Daniel Walker LKML-Reference: <20090814134809.354926067@de.ibm.com> Signed-off-by: Thomas Gleixner --- include/linux/clocksource.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/clocksource.h') diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index f263b3abf46..19ad43af62d 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -213,6 +213,7 @@ extern struct clocksource *clock; /* current clocksource */ #define CLOCK_SOURCE_WATCHDOG 0x10 #define CLOCK_SOURCE_VALID_FOR_HRES 0x20 +#define CLOCK_SOURCE_UNSTABLE 0x40 /* simplify initialization of mask field */ #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1) -- cgit v1.2.3 From 155ec60226ae0ae2aadaa57c951a58a359331030 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Fri, 14 Aug 2009 15:47:26 +0200 Subject: timekeeping: Introduce struct timekeeper Add struct timekeeper to keep the internal values timekeeping.c needs in regard to the currently selected clock source. This moves the timekeeping intervals, xtime_nsec and the ntp error value from struct clocksource to struct timekeeper. The raw_time is removed from the clocksource as well. It gets treated like xtime as a global variable. Eventually xtime raw_time should be moved to struct timekeeper. [ tglx: minor cleanup ] Signed-off-by: Martin Schwidefsky Cc: Ingo Molnar Acked-by: John Stultz Cc: Daniel Walker LKML-Reference: <20090814134809.613209842@de.ibm.com> Signed-off-by: Thomas Gleixner --- include/linux/clocksource.h | 54 ++++----------------------------------------- 1 file changed, 4 insertions(+), 50 deletions(-) (limited to 'include/linux/clocksource.h') diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index 19ad43af62d..e12e3095e2f 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -155,8 +155,6 @@ extern u64 timecounter_cyc2time(struct timecounter *tc, * @flags: flags describing special properties * @vread: vsyscall based read * @resume: resume function for the clocksource, if necessary - * @cycle_interval: Used internally by timekeeping core, please ignore. - * @xtime_interval: Used internally by timekeeping core, please ignore. */ struct clocksource { /* @@ -182,19 +180,12 @@ struct clocksource { #define CLKSRC_FSYS_MMIO_SET(mmio, addr) do { } while (0) #endif - /* timekeeping specific data, ignore */ - cycle_t cycle_interval; - u64 xtime_interval; - u32 raw_interval; /* * Second part is written at each timer interrupt * Keep it in a different cache line to dirty no * more than one cache line. */ cycle_t cycle_last ____cacheline_aligned_in_smp; - u64 xtime_nsec; - s64 error; - struct timespec raw_time; #ifdef CONFIG_CLOCKSOURCE_WATCHDOG /* Watchdog related data, used by the framework */ @@ -203,8 +194,6 @@ struct clocksource { #endif }; -extern struct clocksource *clock; /* current clocksource */ - /* * Clock source flags bits:: */ @@ -270,50 +259,15 @@ static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant) } /** - * cyc2ns - converts clocksource cycles to nanoseconds - * @cs: Pointer to clocksource - * @cycles: Cycles + * clocksource_cyc2ns - converts clocksource cycles to nanoseconds * - * Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds. + * Converts cycles to nanoseconds, using the given mult and shift. * * XXX - This could use some mult_lxl_ll() asm optimization */ -static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles) +static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift) { - u64 ret = (u64)cycles; - ret = (ret * cs->mult) >> cs->shift; - return ret; -} - -/** - * clocksource_calculate_interval - Calculates a clocksource interval struct - * - * @c: Pointer to clocksource. - * @length_nsec: Desired interval length in nanoseconds. - * - * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment - * pair and interval request. - * - * Unless you're the timekeeping code, you should not be using this! - */ -static inline void clocksource_calculate_interval(struct clocksource *c, - unsigned long length_nsec) -{ - u64 tmp; - - /* Do the ns -> cycle conversion first, using original mult */ - tmp = length_nsec; - tmp <<= c->shift; - tmp += c->mult_orig/2; - do_div(tmp, c->mult_orig); - - c->cycle_interval = (cycle_t)tmp; - if (c->cycle_interval == 0) - c->cycle_interval = 1; - - /* Go back from cycles -> shifted ns, this time use ntp adjused mult */ - c->xtime_interval = (u64)c->cycle_interval * c->mult; - c->raw_interval = ((u64)c->cycle_interval * c->mult_orig) >> c->shift; + return ((u64) cycles * mult) >> shift; } -- cgit v1.2.3 From 0a54419836254a27baecd9037103171bcbabaf67 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Fri, 14 Aug 2009 15:47:28 +0200 Subject: timekeeping: Move NTP adjusted clock multiplier to struct timekeeper The clocksource structure has two multipliers, the unmodified multiplier clock->mult_orig and the NTP corrected multiplier clock->mult. The NTP multiplier is misplaced in the struct clocksource, this is private information of the timekeeping code. Add the mult field to the struct timekeeper to contain the NTP corrected value, keep the unmodifed multiplier in clock->mult and remove clock->mult_orig. Signed-off-by: Martin Schwidefsky Cc: Ingo Molnar Acked-by: John Stultz Cc: Daniel Walker LKML-Reference: <20090814134810.149047645@de.ibm.com> Signed-off-by: Thomas Gleixner --- include/linux/clocksource.h | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'include/linux/clocksource.h') diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index e12e3095e2f..e34015effeb 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -149,8 +149,7 @@ extern u64 timecounter_cyc2time(struct timecounter *tc, * @disable: optional function to disable the clocksource * @mask: bitmask for two's complement * subtraction of non 64 bit counters - * @mult: cycle to nanosecond multiplier (adjusted by NTP) - * @mult_orig: cycle to nanosecond multiplier (unadjusted by NTP) + * @mult: cycle to nanosecond multiplier * @shift: cycle to nanosecond divisor (power of two) * @flags: flags describing special properties * @vread: vsyscall based read @@ -168,7 +167,6 @@ struct clocksource { void (*disable)(struct clocksource *cs); cycle_t mask; u32 mult; - u32 mult_orig; u32 shift; unsigned long flags; cycle_t (*vread)(void); -- cgit v1.2.3 From 75c5158f70c065b9704b924503d96e8297838f79 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Fri, 14 Aug 2009 15:47:30 +0200 Subject: timekeeping: Update clocksource with stop_machine update_wall_time calls change_clocksource HZ times per second to check if a new clock source is available. In close to 100% of all calls there is no new clock. Replace the tick based check by an update done with stop_machine. Signed-off-by: Martin Schwidefsky Cc: Ingo Molnar Acked-by: John Stultz Cc: Daniel Walker LKML-Reference: <20090814134810.711836357@de.ibm.com> Signed-off-by: Thomas Gleixner --- include/linux/clocksource.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/clocksource.h') diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index e34015effeb..9ea40ff26f0 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -291,4 +291,6 @@ static inline void update_vsyscall_tz(void) } #endif +extern void timekeeping_notify(struct clocksource *clock); + #endif /* _LINUX_CLOCKSOURCE_H */ -- cgit v1.2.3 From 7285dd7fd375763bfb8ab1ac9cf3f1206f503c16 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Fri, 28 Aug 2009 20:25:24 +0200 Subject: clocksource: Resolve cpu hotplug dead lock with TSC unstable Martin Schwidefsky analyzed it: To register a clocksource the clocksource_mutex is acquired and if necessary timekeeping_notify is called to install the clocksource as the timekeeper clock. timekeeping_notify uses stop_machine which needs to take cpu_add_remove_lock mutex. Starting a new cpu is done with the cpu_add_remove_lock mutex held. native_cpu_up checks the tsc of the new cpu and if the tsc is no good clocksource_change_rating is called. Which needs the clocksource_mutex and the deadlock is complete. The solution is to replace the TSC via the clocksource watchdog mechanism. Mark the TSC as unstable and schedule the watchdog work so it gets removed in the watchdog thread context. Signed-off-by: Thomas Gleixner LKML-Reference: Cc: Martin Schwidefsky Cc: John Stultz --- include/linux/clocksource.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/clocksource.h') diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index 9ea40ff26f0..83d2fbd81b9 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -277,6 +277,7 @@ extern struct clocksource* clocksource_get_next(void); extern void clocksource_change_rating(struct clocksource *cs, int rating); extern void clocksource_resume(void); extern struct clocksource * __init __weak clocksource_default_clock(void); +extern void clocksource_mark_unstable(struct clocksource *cs); #ifdef CONFIG_GENERIC_TIME_VSYSCALL extern void update_vsyscall(struct timespec *ts, struct clocksource *c); -- cgit v1.2.3