Russell King 1b19ca9f0b Fix CPU spinlock lockups on secondary CPU bringup ... Secondary CPU bringup typically calls calibrate_delay() during its initialization. However, calibrate_delay() modifies a global variable (loops_per_jiffy) used for udelay() and __delay(). A side effect of 71c696b1 ("calibrate: extract fall-back calculation into own helper") introduced in the 2.6.39 merge window means that we end up with a substantial period where loops_per_jiffy is zero. This causes the spinlock debugging code to malfunction: u64 loops = loops_per_jiffy * HZ; for (;;) { for (i = 0; i < loops; i++) { if (arch_spin_trylock(&lock->raw_lock)) return; __delay(1); } ... } by never calling arch_spin_trylock() - resulting in the CPU locking up in an infinite loop inside __spin_lock_debug(). Work around this by only writing to loops_per_jiffy only once we have completed all the calibration decisions. Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Cc: <stable@kernel.org> (2.6.39-stable) -- Better solutions (such as omitting the calibration for secondary CPUs, or arranging for calibrate_delay() to return the LPJ value and leave it to the caller to decide where to store it) are a possibility, but would be much more invasive into each architecture. I think this is the best solution for -rc and stable, but it should be revisited for the next merge window. init/calibrate.c | 14 ++++++++------ 1 files changed, 8 insertions(+), 6 deletions(-) Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2011-06-23 08:59:38 -07:00
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calibrate.c	Fix CPU spinlock lockups on secondary CPU bringup	2011-06-23 08:59:38 -07:00
do_mounts_initrd.c	Make do_execve() take a const filename pointer	2010-08-17 18:07:43 -07:00
do_mounts_md.c	init: mark __user address space on string literals	2010-10-26 16:52:15 -07:00
do_mounts_rd.c	init: return proper error code in do_mounts_rd()	2011-03-22 17:44:15 -07:00
do_mounts.c	Fix common misspellings	2011-03-31 11:26:23 -03:00
do_mounts.h	md: move lots of #include lines out of .h files and into .c	2009-03-31 14:33:13 +11:00
initramfs.c	Merge branch 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6	2010-10-28 15:13:55 -07:00
Kconfig	gcov: disable CONFIG_CONSTRUCTORS when not needed by CONFIG_GCOV_KERNEL	2011-06-15 20:04:01 -07:00
main.c	generic-ipi: Fix kexec boot crash by initializing call_single_queue before enabling interrupts	2011-06-17 10:17:12 +02:00
Makefile	kbuild: move compile.h to include/generated	2009-12-12 13:08:14 +01:00
noinitramfs.c	init: mark __user address space on string literals	2010-10-26 16:52:15 -07:00
version.c	userns: add a user_namespace as creator/owner of uts_namespace	2011-03-23 19:46:59 -07:00