From 214e0aed639ef40987bf6159fad303171a6de31e Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Wed, 30 Jul 2014 13:41:55 -0700 Subject: locking/Documentation: Move locking related docs into Documentation/locking/ Specifically: Documentation/locking/lockdep-design.txt Documentation/locking/lockstat.txt Documentation/locking/mutex-design.txt Documentation/locking/rt-mutex-design.txt Documentation/locking/rt-mutex.txt Documentation/locking/spinlocks.txt Documentation/locking/ww-mutex-design.txt Signed-off-by: Davidlohr Bueso Acked-by: Randy Dunlap Signed-off-by: Peter Zijlstra Cc: jason.low2@hp.com Cc: aswin@hp.com Cc: Alexei Starovoitov Cc: Al Viro Cc: Andrew Morton Cc: Chris Mason Cc: Dan Streetman Cc: David Airlie Cc: Davidlohr Bueso Cc: David S. Miller Cc: Greg Kroah-Hartman Cc: Heiko Carstens Cc: Jason Low Cc: Josef Bacik Cc: Kees Cook Cc: Linus Torvalds Cc: Lubomir Rintel Cc: Masanari Iida Cc: Paul E. McKenney Cc: Randy Dunlap Cc: Tim Chen Cc: Vineet Gupta Cc: fengguang.wu@intel.com Link: http://lkml.kernel.org/r/1406752916-3341-6-git-send-email-davidlohr@hp.com Signed-off-by: Ingo Molnar --- lib/Kconfig.debug | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'lib') diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 901096d31c6..9b94a063e26 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -924,7 +924,7 @@ config PROVE_LOCKING the proof of observed correctness is also maintained for an arbitrary combination of these separate locking variants. - For more details, see Documentation/lockdep-design.txt. + For more details, see Documentation/locking/lockdep-design.txt. config LOCKDEP bool @@ -945,7 +945,7 @@ config LOCK_STAT help This feature enables tracking lock contention points - For more details, see Documentation/lockstat.txt + For more details, see Documentation/locking/lockstat.txt This also enables lock events required by "perf lock", subcommand of perf. -- cgit v1.2.3-70-g09d2 From ae17ea0ec7d8fa64fbb773a52b2df5ba4766bcb8 Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Wed, 6 Aug 2014 13:22:02 -0400 Subject: locking/selftest: Support queued rwlock The queued rwlock does not support the use of recursive read-lock in the process context. With changes in the lockdep code to check and disallow recursive read-lock, it is also necessary for the locking selftest to be updated to change the process context recursive read locking results from SUCCESS to FAILURE for rwlock. Signed-off-by: Waiman Long Signed-off-by: Peter Zijlstra Cc: Maarten Lankhorst Cc: Rik van Riel Cc: Scott J Norton Cc: Fengguang Wu Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1407345722-61615-3-git-send-email-Waiman.Long@hp.com Signed-off-by: Ingo Molnar --- lib/locking-selftest.c | 56 +++++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 49 insertions(+), 7 deletions(-) (limited to 'lib') diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index 872a15a2a63..62af709b208 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -267,19 +267,46 @@ GENERATE_TESTCASE(AA_rsem) #undef E /* - * Special-case for read-locking, they are - * allowed to recurse on the same lock class: + * Special-case for read-locking, they are not allowed to + * recurse on the same lock class except under interrupt context: */ static void rlock_AA1(void) { RL(X1); - RL(X1); // this one should NOT fail + RL(X1); // this one should fail } static void rlock_AA1B(void) { RL(X1); - RL(X2); // this one should NOT fail + RL(X2); // this one should fail +} + +static void rlock_AHA1(void) +{ + RL(X1); + HARDIRQ_ENTER(); + RL(X1); // this one should NOT fail + HARDIRQ_EXIT(); +} + +static void rlock_AHA1B(void) +{ + RL(X1); + HARDIRQ_ENTER(); + RL(X2); // this one should NOT fail + HARDIRQ_EXIT(); +} + +static void rlock_ASAHA1(void) +{ + RL(X1); + SOFTIRQ_ENTER(); + RL(X1); // this one should NOT fail + HARDIRQ_ENTER(); + RL(X1); // this one should NOT fail + HARDIRQ_EXIT(); + SOFTIRQ_EXIT(); } static void rsem_AA1(void) @@ -1069,7 +1096,7 @@ static inline void print_testname(const char *testname) print_testname(desc); \ dotest(name##_spin, FAILURE, LOCKTYPE_SPIN); \ dotest(name##_wlock, FAILURE, LOCKTYPE_RWLOCK); \ - dotest(name##_rlock, SUCCESS, LOCKTYPE_RWLOCK); \ + dotest(name##_rlock, FAILURE, LOCKTYPE_RWLOCK); \ dotest(name##_mutex, FAILURE, LOCKTYPE_MUTEX); \ dotest(name##_wsem, FAILURE, LOCKTYPE_RWSEM); \ dotest(name##_rsem, FAILURE, LOCKTYPE_RWSEM); \ @@ -1830,14 +1857,14 @@ void locking_selftest(void) printk(" --------------------------------------------------------------------------\n"); print_testname("recursive read-lock"); printk(" |"); - dotest(rlock_AA1, SUCCESS, LOCKTYPE_RWLOCK); + dotest(rlock_AA1, FAILURE, LOCKTYPE_RWLOCK); printk(" |"); dotest(rsem_AA1, FAILURE, LOCKTYPE_RWSEM); printk("\n"); print_testname("recursive read-lock #2"); printk(" |"); - dotest(rlock_AA1B, SUCCESS, LOCKTYPE_RWLOCK); + dotest(rlock_AA1B, FAILURE, LOCKTYPE_RWLOCK); printk(" |"); dotest(rsem_AA1B, FAILURE, LOCKTYPE_RWSEM); printk("\n"); @@ -1856,6 +1883,21 @@ void locking_selftest(void) dotest(rsem_AA3, FAILURE, LOCKTYPE_RWSEM); printk("\n"); + print_testname("recursive rlock with interrupt"); + printk(" |"); + dotest(rlock_AHA1, SUCCESS, LOCKTYPE_RWLOCK); + printk("\n"); + + print_testname("recursive rlock with interrupt #2"); + printk(" |"); + dotest(rlock_AHA1B, SUCCESS, LOCKTYPE_RWLOCK); + printk("\n"); + + print_testname("recursive rlock with interrupt #3"); + printk(" |"); + dotest(rlock_ASAHA1, SUCCESS, LOCKTYPE_RWLOCK); + printk("\n"); + printk(" --------------------------------------------------------------------------\n"); /* -- cgit v1.2.3-70-g09d2 From 8acd91e8620836a56ff62028ed28ba629f2881a0 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 30 Sep 2014 15:26:00 +0200 Subject: locking/lockdep: Revert qrwlock recusive stuff Commit f0bab73cb539 ("locking/lockdep: Restrict the use of recursive read_lock() with qrwlock") changed lockdep to try and conform to the qrwlock semantics which differ from the traditional rwlock semantics. In particular qrwlock is fair outside of interrupt context, but in interrupt context readers will ignore all fairness. The problem modeling this is that read and write side have different lock state (interrupts) semantics but we only have a single representation of these. Therefore lockdep will get confused, thinking the lock can cause interrupt lock inversions. So revert it for now; the old rwlock semantics were already imperfectly modeled and the qrwlock extra won't fit either. If we want to properly fix this, I think we need to resurrect the work by Gautham did a few years ago that split the read and write state of locks: http://lwn.net/Articles/332801/ FWIW the locking selftest that would've failed (and was reported by Borislav earlier) is something like: RL(X1); /* IRQ-ON */ LOCK(A); UNLOCK(A); RU(X1); IRQ_ENTER(); RL(X1); /* IN-IRQ */ RU(X1); IRQ_EXIT(); At which point it would report that because A is an IRQ-unsafe lock we can suffer the following inversion: CPU0 CPU1 lock(A) lock(X1) lock(A) lock(X1) And this is 'wrong' because X1 can recurse (assuming the above lock are in fact read-lock) but lockdep doesn't know about this. Signed-off-by: Peter Zijlstra (Intel) Cc: Waiman Long Cc: ego@linux.vnet.ibm.com Cc: bp@alien8.de Cc: Linus Torvalds Cc: Paul E. McKenney Link: http://lkml.kernel.org/r/20140930132600.GA7444@worktop.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- include/linux/lockdep.h | 10 +-------- kernel/locking/lockdep.c | 6 ------ lib/locking-selftest.c | 56 ++++++------------------------------------------ 3 files changed, 8 insertions(+), 64 deletions(-) (limited to 'lib') diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index b5a84b62fb8..f388481201c 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -478,24 +478,16 @@ static inline void print_irqtrace_events(struct task_struct *curr) * on the per lock-class debug mode: */ -/* - * Read states in the 2-bit held_lock:read field: - * 0: Exclusive lock - * 1: Shareable lock, cannot be recursively called - * 2: Shareable lock, can be recursively called - * 3: Shareable lock, cannot be recursively called except in interrupt context - */ #define lock_acquire_exclusive(l, s, t, n, i) lock_acquire(l, s, t, 0, 1, n, i) #define lock_acquire_shared(l, s, t, n, i) lock_acquire(l, s, t, 1, 1, n, i) #define lock_acquire_shared_recursive(l, s, t, n, i) lock_acquire(l, s, t, 2, 1, n, i) -#define lock_acquire_shared_irecursive(l, s, t, n, i) lock_acquire(l, s, t, 3, 1, n, i) #define spin_acquire(l, s, t, i) lock_acquire_exclusive(l, s, t, NULL, i) #define spin_acquire_nest(l, s, t, n, i) lock_acquire_exclusive(l, s, t, n, i) #define spin_release(l, n, i) lock_release(l, n, i) #define rwlock_acquire(l, s, t, i) lock_acquire_exclusive(l, s, t, NULL, i) -#define rwlock_acquire_read(l, s, t, i) lock_acquire_shared_irecursive(l, s, t, NULL, i) +#define rwlock_acquire_read(l, s, t, i) lock_acquire_shared_recursive(l, s, t, NULL, i) #define rwlock_release(l, n, i) lock_release(l, n, i) #define seqcount_acquire(l, s, t, i) lock_acquire_exclusive(l, s, t, NULL, i) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 420ba685c4e..88d0d4420ad 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -3597,12 +3597,6 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass, raw_local_irq_save(flags); check_flags(flags); - /* - * An interrupt recursive read in interrupt context can be considered - * to be the same as a recursive read from checking perspective. - */ - if ((read == 3) && in_interrupt()) - read = 2; current->lockdep_recursion = 1; trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip); __lock_acquire(lock, subclass, trylock, read, check, diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index 62af709b208..872a15a2a63 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -267,46 +267,19 @@ GENERATE_TESTCASE(AA_rsem) #undef E /* - * Special-case for read-locking, they are not allowed to - * recurse on the same lock class except under interrupt context: + * Special-case for read-locking, they are + * allowed to recurse on the same lock class: */ static void rlock_AA1(void) { RL(X1); - RL(X1); // this one should fail + RL(X1); // this one should NOT fail } static void rlock_AA1B(void) { RL(X1); - RL(X2); // this one should fail -} - -static void rlock_AHA1(void) -{ - RL(X1); - HARDIRQ_ENTER(); - RL(X1); // this one should NOT fail - HARDIRQ_EXIT(); -} - -static void rlock_AHA1B(void) -{ - RL(X1); - HARDIRQ_ENTER(); - RL(X2); // this one should NOT fail - HARDIRQ_EXIT(); -} - -static void rlock_ASAHA1(void) -{ - RL(X1); - SOFTIRQ_ENTER(); - RL(X1); // this one should NOT fail - HARDIRQ_ENTER(); - RL(X1); // this one should NOT fail - HARDIRQ_EXIT(); - SOFTIRQ_EXIT(); + RL(X2); // this one should NOT fail } static void rsem_AA1(void) @@ -1096,7 +1069,7 @@ static inline void print_testname(const char *testname) print_testname(desc); \ dotest(name##_spin, FAILURE, LOCKTYPE_SPIN); \ dotest(name##_wlock, FAILURE, LOCKTYPE_RWLOCK); \ - dotest(name##_rlock, FAILURE, LOCKTYPE_RWLOCK); \ + dotest(name##_rlock, SUCCESS, LOCKTYPE_RWLOCK); \ dotest(name##_mutex, FAILURE, LOCKTYPE_MUTEX); \ dotest(name##_wsem, FAILURE, LOCKTYPE_RWSEM); \ dotest(name##_rsem, FAILURE, LOCKTYPE_RWSEM); \ @@ -1857,14 +1830,14 @@ void locking_selftest(void) printk(" --------------------------------------------------------------------------\n"); print_testname("recursive read-lock"); printk(" |"); - dotest(rlock_AA1, FAILURE, LOCKTYPE_RWLOCK); + dotest(rlock_AA1, SUCCESS, LOCKTYPE_RWLOCK); printk(" |"); dotest(rsem_AA1, FAILURE, LOCKTYPE_RWSEM); printk("\n"); print_testname("recursive read-lock #2"); printk(" |"); - dotest(rlock_AA1B, FAILURE, LOCKTYPE_RWLOCK); + dotest(rlock_AA1B, SUCCESS, LOCKTYPE_RWLOCK); printk(" |"); dotest(rsem_AA1B, FAILURE, LOCKTYPE_RWSEM); printk("\n"); @@ -1883,21 +1856,6 @@ void locking_selftest(void) dotest(rsem_AA3, FAILURE, LOCKTYPE_RWSEM); printk("\n"); - print_testname("recursive rlock with interrupt"); - printk(" |"); - dotest(rlock_AHA1, SUCCESS, LOCKTYPE_RWLOCK); - printk("\n"); - - print_testname("recursive rlock with interrupt #2"); - printk(" |"); - dotest(rlock_AHA1B, SUCCESS, LOCKTYPE_RWLOCK); - printk("\n"); - - print_testname("recursive rlock with interrupt #3"); - printk(" |"); - dotest(rlock_ASAHA1, SUCCESS, LOCKTYPE_RWLOCK); - printk("\n"); - printk(" --------------------------------------------------------------------------\n"); /* -- cgit v1.2.3-70-g09d2