From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Luck, Tony" Date: Thu, 16 Sep 2010 20:23:14 +0000 Subject: [IA64 PATCH for v2.6.32 to v2.6.35] ia64: fix siglock in fsys_rt_sigprocmask Message-Id: <4c927cb2184948077a@agluck-desktop.sc.intel.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org 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 Signed-off-by: Tony Luck --- 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 diff --git a/arch/ia64/kernel/fsys.S b/arch/ia64/kernel/fsys.S index 3567d54..331d42b 100644 --- a/arch/ia64/kernel/fsys.S +++ b/arch/ia64/kernel/fsys.S @@ -420,22 +420,31 @@ EX(.fail_efault, ld8 r14=[r33]) // r14 <- *set ;; RSM_PSR_I(p0, r18, r19) // mask interrupt delivery - mov ar.ccv=0 andcm r14=r14,r17 // filter out SIGKILL & SIGSTOP + mov r8=EINVAL // default to EINVAL #ifdef CONFIG_SMP - mov r17=1 + // __ticket_spin_trylock(r31) + ld4 r17=[r31] ;; - cmpxchg4.acq r18=[r31],r17,ar.ccv // try to acquire the lock - mov r8=EINVAL // default to EINVAL + mov.m ar.ccv=r17 + extr.u r9=r17,17,15 + adds r19=1,r17 + extr.u r18=r17,0,15 + ;; + cmp.eq p6,p7=r9,r18 ;; +(p6) cmpxchg4.acq r9=[r31],r19,ar.ccv +(p6) dep.z r20=r19,1,15 // next serving ticket for unlock +(p7) br.cond.spnt.many .lock_contention + ;; + cmp4.eq p0,p7=r9,r17 + adds r31=2,r31 +(p7) br.cond.spnt.many .lock_contention ld8 r3=[r2] // re-read current->blocked now that we hold the lock - cmp4.ne p6,p0=r18,r0 -(p6) br.cond.spnt.many .lock_contention ;; #else ld8 r3=[r2] // re-read current->blocked now that we hold the lock - mov r8=EINVAL // default to EINVAL #endif add r18=IA64_TASK_PENDING_OFFSET+IA64_SIGPENDING_SIGNAL_OFFSET,r16 add r19=IA64_TASK_SIGNAL_OFFSET,r16 @@ -490,7 +499,9 @@ EX(.fail_efault, ld8 r14=[r33]) // r14 <- *set (p6) br.cond.spnt.few 1b // yes -> retry #ifdef CONFIG_SMP - st4.rel [r31]=r0 // release the lock + // __ticket_spin_unlock(r31) + st2.rel [r31]=r20 + mov r20=0 // i must not leak kernel bits... #endif SSM_PSR_I(p0, p9, r31) ;; @@ -512,7 +523,8 @@ EX(.fail_efault, (p15) st8 [r34]=r3) .sig_pending: #ifdef CONFIG_SMP - st4.rel [r31]=r0 // release the lock + // __ticket_spin_unlock(r31) + st2.rel [r31]=r20 // release the lock #endif SSM_PSR_I(p0, p9, r17) ;;