On Thu, Sep 16, 2010 at 01:23:14PM -0700, Luck, Tony wrote: > 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. > > Fix to use the new ticket lock algorithm. > > Cc: Petr Tesarik <ptesarik@xxxxxxx> > Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx> > > --- > > This went upstream in two pieces - there was a bug in the first attempt > (my code), the second (by Petr) fixes the bug (and also makes the code > much prettier). Patch below is the combination of both so we don't > make a bisection trap for people to fall into. If this violates stable > rules, then feel free to just cherry pick the two commits. > > commit f574c843191728d9407b766a027f779dcd27b272 > [IA64] fix siglock > commit 2d2b6901649a62977452be85df53eda2412def24 > [IA64] Optimize ticket spinlocks in fsys_rt_sigprocmask I just applied these two patches in-order, to make it more obvious as to where things came from. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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