#include #include #include /* * An MCS like lock especially tailored for optimistic spinning for sleeping * lock implementations (mutex, rwsem, etc). * * Using a single mcs node per CPU is safe because sleeping locks should not be * called from interrupt context and we have preemption disabled while * spinning. */ static DEFINE_PER_CPU_SHARED_ALIGNED(struct optimistic_spin_node, osq_node); /* * We use the value 0 to represent "no CPU", thus the encoded value * will be the CPU number incremented by 1. */ static inline int encode_cpu(int cpu_nr) { return cpu_nr + 1; } static inline int node_cpu(struct optimistic_spin_node *node) { return node->cpu - 1; } static inline struct optimistic_spin_node *decode_cpu(int encoded_cpu_val) { int cpu_nr = encoded_cpu_val - 1; return per_cpu_ptr(&osq_node, cpu_nr); } /* * Get a stable @node->next pointer, either for unlock() or unqueue() purposes. * Can return NULL in case we were the last queued and we updated @lock instead. */ static inline struct optimistic_spin_node * osq_wait_next(struct optimistic_spin_queue *lock, struct optimistic_spin_node *node, struct optimistic_spin_node *prev) { struct optimistic_spin_node *next = NULL; int curr = encode_cpu(smp_processor_id()); int old; /* * If there is a prev node in queue, then the 'old' value will be * the prev node's CPU #, else it's set to OSQ_UNLOCKED_VAL since if * we're currently last in queue, then the queue will then become empty. */ old = prev ? prev->cpu : OSQ_UNLOCKED_VAL; for (;;) { if (atomic_read(&lock->tail) == curr && atomic_cmpxchg_acquire(&lock->tail, curr, old) == curr) { /* * We were the last queued, we moved @lock back. @prev * will now observe @lock and will complete its * unlock()/unqueue(). */ break; } /* * We must xchg() the @node->next value, because if we were to * leave it in, a concurrent unlock()/unqueue() from * @node->next might complete Step-A and think its @prev is * still valid. * * If the concurrent unlock()/unqueue() wins the race, we'll * wait for either @lock to point to us, through its Step-B, or * wait for a new @node->next from its Step-C. */ if (node->next) { next = xchg(&node->next, NULL); if (next) break; } cpu_relax(); } return next; } bool osq_lock(struct optimistic_spin_queue *lock) { struct optimistic_spin_node *node = this_cpu_ptr(&osq_node); struct optimistic_spin_node *prev, *next; int curr = encode_cpu(smp_processor_id()); int old; node->locked = 0; node->next = NULL; node->cpu = curr; /* * We need both ACQUIRE (pairs with corresponding RELEASE in * unlock() uncontended, or fastpath) and RELEASE (to publish * the node fields we just initialised) semantics when updating * the lock tail. */ old = atomic_xchg(&lock->tail, curr); if (old == OSQ_UNLOCKED_VAL) return true; prev = decode_cpu(old); node->prev = prev; WRITE_ONCE(prev->next, node); /* * Normally @prev is untouchable after the above store; because at that * moment unlock can proceed and wipe the node element from stack. * * However, since our nodes are static per-cpu storage, we're * guaranteed their existence -- this allows us to apply * cmpxchg in an attempt to undo our queueing. */ while (!READ_ONCE(node->locked)) { /* * If we need to reschedule bail... so we can block. * Use vcpu_is_preempted() to avoid waiting for a preempted * lock holder: */ if (need_resched() || vcpu_is_preempted(node_cpu(node->prev))) goto unqueue; cpu_relax(); } return true; unqueue: /* * Step - A -- stabilize @prev * * Undo our @prev->next assignment; this will make @prev's * unlock()/unqueue() wait for a next pointer since @lock points to us * (or later). */ for (;;) { if (prev->next == node && cmpxchg(&prev->next, node, NULL) == node) break; /* * We can only fail the cmpxchg() racing against an unlock(), * in which case we should observe @node->locked becomming * true. */ if (smp_load_acquire(&node->locked)) return true; cpu_relax(); /* * Or we race against a concurrent unqueue()'s step-B, in which * case its step-C will write us a new @node->prev pointer. */ prev = READ_ONCE(node->prev); } /* * Step - B -- stabilize @next * * Similar to unlock(), wait for @node->next or move @lock from @node * back to @prev. */ next = osq_wait_next(lock, node, prev); if (!next) return false; /* * Step - C -- unlink * * @prev is stable because its still waiting for a new @prev->next * pointer, @next is stable because our @node->next pointer is NULL and * it will wait in Step-A. */ WRITE_ONCE(next->prev, prev); WRITE_ONCE(prev->next, next); return false; } void osq_unlock(struct optimistic_spin_queue *lock) { struct optimistic_spin_node *node, *next; int curr = encode_cpu(smp_processor_id()); /* * Fast path for the uncontended case. */ if (likely(atomic_cmpxchg_release(&lock->tail, curr, OSQ_UNLOCKED_VAL) == curr)) return; /* * Second most likely case. */ node = this_cpu_ptr(&osq_node); next = xchg(&node->next, NULL); if (next) { WRITE_ONCE(next->locked, 1); return; } next = osq_wait_next(lock, node, NULL); if (next) WRITE_ONCE(next->locked, 1); } t-next.git/tree/include/net/sch_generic.h?id=dfef358bd1beb4e7b5c94eca944be9cd23dfc752'>include/net/sch_generic.h parent030305d69fc6963c16003f50d7e8d74b02d0a143 (diff)
PCI/MSI: Don't apply affinity if there aren't enough vectors left
Bart reported a problem wіth an out of bounds access in the low-level IRQ affinity code, which we root caused to the qla2xxx driver assigning all its MSI-X vectors to the pre and post vectors, and not having any left for the actually spread IRQs. Fix this issue by not asking for affinity assignment when there are no vectors to assign left. Fixes: 402723ad5c62 ("PCI/MSI: Provide pci_alloc_irq_vectors_affinity()") Link: https://lkml.kernel.org/r/1485359225.3093.3.camel@sandisk.com Reported-by: Bart Van Assche <bart.vanassche@sandisk.com> Tested-by: Bart Van Assche <bart.vanassche@sandisk.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Diffstat (limited to 'include/net/sch_generic.h')