tree 61f464091fa4d59a2782c2c746ebadc766566fd3
parent d56557af19867edb8c0e96f8e26399698a08857f
author Tony Luck <tony.luck@intel.com> 1284070616 -0700
committer Tony Luck <tony.luck@intel.com> 1284070616 -0700

[IA64] fix siglock

When ia64 converted to using ticket locks, an inline implementation
of trylock/unlock in fsys.S was missed.  This was not noticed because
in most circumstances it simply resulted in using the slow path because
the siglock was apparently not available (under old spinlock rules).

Problems occur when the ticket spinlock has value 0x0 (when first
initialised, or when it wraps around). At this point the fsys.S
code acquires the lock (changing the 0x0 to 0x1. If another process
attempts to get the lock at this point, it will change the value from
0x1 to 0x2 (using new ticket lock rules). Then the fsys.S code will
free the lock using old spinlock rules by writing 0x0 to it. From
here a variety of bad things can happen.

Signed-off-by: Tony Luck <tony.luck@intel.com>