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authorPeter Zijlstra <peterz@infradead.org>2017-01-19 14:36:33 +0100
committerIngo Molnar <mingo@kernel.org>2017-01-20 02:38:46 +0100
commitacb04058de49458010c44bb35b849d45113fd668 (patch)
tree6011ca77b47f21fcd5e65e5a2f02dddadd3f950c /arch/parisc/kernel/setup.c
parentsched/x86: Remove unnecessary TBM3 check to update topology (diff)
downloadlinux-dev-acb04058de49458010c44bb35b849d45113fd668.tar.xz
linux-dev-acb04058de49458010c44bb35b849d45113fd668.zip
sched/clock: Fix hotplug crash
Mike reported that he could trigger the WARN_ON_ONCE() in set_sched_clock_stable() using hotplug. This exposed a fundamental problem with the interface, we should never mark the TSC stable if we ever find it to be unstable. Therefore set_sched_clock_stable() is a broken interface. The reason it existed is that not having it is a pain, it means all relevant architecture code needs to call clear_sched_clock_stable() where appropriate. Of the three architectures that select HAVE_UNSTABLE_SCHED_CLOCK ia64 and parisc are trivial in that they never called set_sched_clock_stable(), so add an unconditional call to clear_sched_clock_stable() to them. For x86 the story is a lot more involved, and what this patch tries to do is ensure we preserve the status quo. So even is Cyrix or Transmeta have usable TSC they never called set_sched_clock_stable() so they now get an explicit mark unstable. Reported-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 9881b024b7d7 ("sched/clock: Delay switching sched_clock to stable") Link: http://lkml.kernel.org/r/20170119133633.GB6536@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to '')
-rw-r--r--arch/parisc/kernel/setup.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/parisc/kernel/setup.c b/arch/parisc/kernel/setup.c
index 2e66a887788e..068ed3607bac 100644
--- a/arch/parisc/kernel/setup.c
+++ b/arch/parisc/kernel/setup.c
@@ -36,6 +36,7 @@
#undef PCI_DEBUG
#include <linux/proc_fs.h>
#include <linux/export.h>
+#include <linux/sched.h>
#include <asm/processor.h>
#include <asm/sections.h>
@@ -176,6 +177,7 @@ void __init setup_arch(char **cmdline_p)
conswitchp = &dummy_con; /* we use do_take_over_console() later ! */
#endif
+ clear_sched_clock_stable();
}
/*