From 3896c329df8092661dac80f55a8c3f60136fd61a Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 24 Jun 2014 14:48:19 +0200 Subject: [PATCH 1/2] x86, tsc: Fix cpufreq lockup Mauro reported that his AMD X2 using the powernow-k8 cpufreq driver locked up when doing cpu hotplug. Because we called set_cyc2ns_scale() from the time_cpufreq_notifier() unconditionally, it gets called multiple times for each freq change, instead of only the once, when the tsc_khz value actually changes. Because it gets called more than once, we run out of cyc2ns data slots and stall, waiting for a free one, but because we're half way offline, there's no consumers to free slots. By placing the call inside the condition that actually changes tsc_khz we avoid superfluous calls and avoid the problem. Reported-by: Mauro Tested-by: Mauro Fixes: 20d1c86a5776 ("sched/clock, x86: Rewrite cyc2ns() to avoid the need to disable IRQs") Cc: Cc: "Rafael J. Wysocki" Cc: Viresh Kumar Cc: Bin Gao Cc: Linus Torvalds Cc: Mika Westerberg Cc: Paul Gortmaker Cc: Stefani Seibold Cc: linux-kernel@vger.kernel.org Signed-off-by: Peter Zijlstra Signed-off-by: Ingo Molnar --- arch/x86/kernel/tsc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 57e5ce126d5a..ea030319b321 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -920,9 +920,9 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new); if (!(freq->flags & CPUFREQ_CONST_LOOPS)) mark_tsc_unstable("cpufreq changes"); - } - set_cyc2ns_scale(tsc_khz, freq->cpu); + set_cyc2ns_scale(tsc_khz, freq->cpu); + } return 0; } From b6220ad66bcd4a50737eb3c08e9466aa44f3bc98 Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Tue, 24 Jun 2014 18:05:29 -0700 Subject: [PATCH 2/2] sched: Fix compiler warnings Commit 143e1e28cb (sched: Rework sched_domain topology definition) introduced a number of functions with a return value of 'const int'. gcc doesn't know what to do with that and, if the kernel is compiled with W=1, complains with the following warnings whenever sched.h is included. include/linux/sched.h:875:25: warning: type qualifiers ignored on function return type include/linux/sched.h:882:25: warning: type qualifiers ignored on function return type include/linux/sched.h:889:25: warning: type qualifiers ignored on function return type include/linux/sched.h:1002:21: warning: type qualifiers ignored on function return type Commits fb2aa855 (sched, ARM: Create a dedicated scheduler topology table) and 607b45e9a (sched, powerpc: Create a dedicated topology table) introduce the same warning in the arm and powerpc code. Drop 'const' from the function declarations to fix the problem. The fix for all three patches has to be applied together to avoid compilation failures for the affected architectures. Acked-by: Vincent Guittot Acked-by: Benjamin Herrenschmidt Signed-off-by: Guenter Roeck Cc: Russell King Cc: Paul Mackerras Cc: Dietmar Eggemann Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1403658329-13196-1-git-send-email-linux@roeck-us.net Signed-off-by: Ingo Molnar --- arch/arm/kernel/topology.c | 2 +- arch/powerpc/kernel/smp.c | 2 +- include/linux/sched.h | 8 ++++---- 3 files changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c index 9d853189028b..e35d880f9773 100644 --- a/arch/arm/kernel/topology.c +++ b/arch/arm/kernel/topology.c @@ -275,7 +275,7 @@ void store_cpu_topology(unsigned int cpuid) cpu_topology[cpuid].socket_id, mpidr); } -static inline const int cpu_corepower_flags(void) +static inline int cpu_corepower_flags(void) { return SD_SHARE_PKG_RESOURCES | SD_SHARE_POWERDOMAIN; } diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c index 51a3ff78838a..1007fb802e6b 100644 --- a/arch/powerpc/kernel/smp.c +++ b/arch/powerpc/kernel/smp.c @@ -747,7 +747,7 @@ int setup_profiling_timer(unsigned int multiplier) #ifdef CONFIG_SCHED_SMT /* cpumask of CPUs with asymetric SMT dependancy */ -static const int powerpc_smt_flags(void) +static int powerpc_smt_flags(void) { int flags = SD_SHARE_CPUCAPACITY | SD_SHARE_PKG_RESOURCES; diff --git a/include/linux/sched.h b/include/linux/sched.h index 306f4f0c987a..0376b054a0d0 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -872,21 +872,21 @@ enum cpu_idle_type { #define SD_NUMA 0x4000 /* cross-node balancing */ #ifdef CONFIG_SCHED_SMT -static inline const int cpu_smt_flags(void) +static inline int cpu_smt_flags(void) { return SD_SHARE_CPUCAPACITY | SD_SHARE_PKG_RESOURCES; } #endif #ifdef CONFIG_SCHED_MC -static inline const int cpu_core_flags(void) +static inline int cpu_core_flags(void) { return SD_SHARE_PKG_RESOURCES; } #endif #ifdef CONFIG_NUMA -static inline const int cpu_numa_flags(void) +static inline int cpu_numa_flags(void) { return SD_NUMA; } @@ -999,7 +999,7 @@ void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms); bool cpus_share_cache(int this_cpu, int that_cpu); typedef const struct cpumask *(*sched_domain_mask_f)(int cpu); -typedef const int (*sched_domain_flags_f)(void); +typedef int (*sched_domain_flags_f)(void); #define SDTL_OVERLAP 0x01