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97d052ea3f
- Untangle the header spaghetti which causes build failures in various situations caused by the lockdep additions to seqcount to validate that the write side critical sections are non-preemptible. - The seqcount associated lock debug addons which were blocked by the above fallout. seqcount writers contrary to seqlock writers must be externally serialized, which usually happens via locking - except for strict per CPU seqcounts. As the lock is not part of the seqcount, lockdep cannot validate that the lock is held. This new debug mechanism adds the concept of associated locks. sequence count has now lock type variants and corresponding initializers which take a pointer to the associated lock used for writer serialization. If lockdep is enabled the pointer is stored and write_seqcount_begin() has a lockdep assertion to validate that the lock is held. Aside of the type and the initializer no other code changes are required at the seqcount usage sites. The rest of the seqcount API is unchanged and determines the type at compile time with the help of _Generic which is possible now that the minimal GCC version has been moved up. Adding this lockdep coverage unearthed a handful of seqcount bugs which have been addressed already independent of this. While generaly useful this comes with a Trojan Horse twist: On RT kernels the write side critical section can become preemtible if the writers are serialized by an associated lock, which leads to the well known reader preempts writer livelock. RT prevents this by storing the associated lock pointer independent of lockdep in the seqcount and changing the reader side to block on the lock when a reader detects that a writer is in the write side critical section. - Conversion of seqcount usage sites to associated types and initializers. -----BEGIN PGP SIGNATURE----- iQJHBAABCgAxFiEEQp8+kY+LLUocC4bMphj1TA10mKEFAl8xmPYTHHRnbHhAbGlu dXRyb25peC5kZQAKCRCmGPVMDXSYoTuQEACyzQCjU8PgehPp9oMqWzaX2fcVyuZO QU2yw6gmz2oTz3ZHUNwdW8UnzGh2OWosK3kDruoD9FtSS51lER1/ISfSPCGfyqxC KTjOcB1Kvxwq/3LcCx7Zi3ZxWApat74qs3EhYhKtEiQ2Y9xv9rLq8VV1UWAwyxq0 eHpjlIJ6b6rbt+ARslaB7drnccOsdK+W/roNj4kfyt+gezjBfojGRdMGQNMFcpnv shuTC+vYurAVIiVA/0IuizgHfwZiXOtVpjVoEWaxg6bBH6HNuYMYzdSa/YrlDkZs n/aBI/Xkvx+Eacu8b1Zwmbzs5EnikUK/2dMqbzXKUZK61eV4hX5c2xrnr1yGWKTs F/juh69Squ7X6VZyKVgJ9RIccVueqwR2EprXWgH3+RMice5kjnXH4zURp0GHALxa DFPfB6fawcH3Ps87kcRFvjgm6FBo0hJ1AxmsW1dY4ACFB9azFa2euW+AARDzHOy2 VRsUdhL9CGwtPjXcZ/9Rhej6fZLGBXKr8uq5QiMuvttp4b6+j9FEfBgD4S6h8csl AT2c2I9LcbWqyUM9P4S7zY/YgOZw88vHRuDH7tEBdIeoiHfrbSBU7EQ9jlAKq/59 f+Htu2Io281c005g7DEeuCYvpzSYnJnAitj5Lmp/kzk2Wn3utY1uIAVszqwf95Ul 81ppn2KlvzUK8g== =7Gj+ -----END PGP SIGNATURE----- Merge tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull locking updates from Thomas Gleixner: "A set of locking fixes and updates: - Untangle the header spaghetti which causes build failures in various situations caused by the lockdep additions to seqcount to validate that the write side critical sections are non-preemptible. - The seqcount associated lock debug addons which were blocked by the above fallout. seqcount writers contrary to seqlock writers must be externally serialized, which usually happens via locking - except for strict per CPU seqcounts. As the lock is not part of the seqcount, lockdep cannot validate that the lock is held. This new debug mechanism adds the concept of associated locks. sequence count has now lock type variants and corresponding initializers which take a pointer to the associated lock used for writer serialization. If lockdep is enabled the pointer is stored and write_seqcount_begin() has a lockdep assertion to validate that the lock is held. Aside of the type and the initializer no other code changes are required at the seqcount usage sites. The rest of the seqcount API is unchanged and determines the type at compile time with the help of _Generic which is possible now that the minimal GCC version has been moved up. Adding this lockdep coverage unearthed a handful of seqcount bugs which have been addressed already independent of this. While generally useful this comes with a Trojan Horse twist: On RT kernels the write side critical section can become preemtible if the writers are serialized by an associated lock, which leads to the well known reader preempts writer livelock. RT prevents this by storing the associated lock pointer independent of lockdep in the seqcount and changing the reader side to block on the lock when a reader detects that a writer is in the write side critical section. - Conversion of seqcount usage sites to associated types and initializers" * tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits) locking/seqlock, headers: Untangle the spaghetti monster locking, arch/ia64: Reduce <asm/smp.h> header dependencies by moving XTP bits into the new <asm/xtp.h> header x86/headers: Remove APIC headers from <asm/smp.h> seqcount: More consistent seqprop names seqcount: Compress SEQCNT_LOCKNAME_ZERO() seqlock: Fold seqcount_LOCKNAME_init() definition seqlock: Fold seqcount_LOCKNAME_t definition seqlock: s/__SEQ_LOCKDEP/__SEQ_LOCK/g hrtimer: Use sequence counter with associated raw spinlock kvm/eventfd: Use sequence counter with associated spinlock userfaultfd: Use sequence counter with associated spinlock NFSv4: Use sequence counter with associated spinlock iocost: Use sequence counter with associated spinlock raid5: Use sequence counter with associated spinlock vfs: Use sequence counter with associated spinlock timekeeping: Use sequence counter with associated raw spinlock xfrm: policy: Use sequence counters with associated lock netfilter: nft_set_rbtree: Use sequence counter with associated rwlock netfilter: conntrack: Use sequence counter with associated spinlock sched: tasks: Use sequence counter with associated spinlock ...
342 lines
7.3 KiB
C
342 lines
7.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* SMP Support
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*
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* Copyright (C) 1999 Walt Drummond <drummond@valinux.com>
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* Copyright (C) 1999, 2001, 2003 David Mosberger-Tang <davidm@hpl.hp.com>
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*
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* Lots of stuff stolen from arch/alpha/kernel/smp.c
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*
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* 01/05/16 Rohit Seth <rohit.seth@intel.com> IA64-SMP functions. Reorganized
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* the existing code (on the lines of x86 port).
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* 00/09/11 David Mosberger <davidm@hpl.hp.com> Do loops_per_jiffy
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* calibration on each CPU.
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* 00/08/23 Asit Mallick <asit.k.mallick@intel.com> fixed logical processor id
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* 00/03/31 Rohit Seth <rohit.seth@intel.com> Fixes for Bootstrap Processor
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* & cpu_online_map now gets done here (instead of setup.c)
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* 99/10/05 davidm Update to bring it in sync with new command-line processing
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* scheme.
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* 10/13/00 Goutham Rao <goutham.rao@intel.com> Updated smp_call_function and
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* smp_call_function_single to resend IPI on timeouts
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/init.h>
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#include <linux/interrupt.h>
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#include <linux/smp.h>
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#include <linux/kernel_stat.h>
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#include <linux/mm.h>
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#include <linux/cache.h>
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#include <linux/delay.h>
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#include <linux/efi.h>
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#include <linux/bitops.h>
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#include <linux/kexec.h>
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#include <linux/atomic.h>
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#include <asm/current.h>
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#include <asm/delay.h>
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#include <asm/io.h>
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#include <asm/irq.h>
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#include <asm/page.h>
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#include <asm/processor.h>
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#include <asm/ptrace.h>
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#include <asm/sal.h>
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#include <asm/tlbflush.h>
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#include <asm/unistd.h>
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#include <asm/mca.h>
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#include <asm/xtp.h>
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/*
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* Note: alignment of 4 entries/cacheline was empirically determined
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* to be a good tradeoff between hot cachelines & spreading the array
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* across too many cacheline.
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*/
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static struct local_tlb_flush_counts {
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unsigned int count;
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} __attribute__((__aligned__(32))) local_tlb_flush_counts[NR_CPUS];
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static DEFINE_PER_CPU_SHARED_ALIGNED(unsigned short [NR_CPUS],
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shadow_flush_counts);
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#define IPI_CALL_FUNC 0
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#define IPI_CPU_STOP 1
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#define IPI_CALL_FUNC_SINGLE 2
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#define IPI_KDUMP_CPU_STOP 3
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/* This needs to be cacheline aligned because it is written to by *other* CPUs. */
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static DEFINE_PER_CPU_SHARED_ALIGNED(unsigned long, ipi_operation);
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extern void cpu_halt (void);
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static void
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stop_this_cpu(void)
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{
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/*
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* Remove this CPU:
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*/
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set_cpu_online(smp_processor_id(), false);
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max_xtp();
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local_irq_disable();
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cpu_halt();
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}
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void
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cpu_die(void)
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{
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max_xtp();
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local_irq_disable();
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cpu_halt();
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/* Should never be here */
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BUG();
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for (;;);
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}
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irqreturn_t
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handle_IPI (int irq, void *dev_id)
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{
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int this_cpu = get_cpu();
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unsigned long *pending_ipis = &__ia64_per_cpu_var(ipi_operation);
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unsigned long ops;
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mb(); /* Order interrupt and bit testing. */
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while ((ops = xchg(pending_ipis, 0)) != 0) {
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mb(); /* Order bit clearing and data access. */
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do {
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unsigned long which;
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which = ffz(~ops);
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ops &= ~(1 << which);
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switch (which) {
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case IPI_CPU_STOP:
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stop_this_cpu();
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break;
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case IPI_CALL_FUNC:
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generic_smp_call_function_interrupt();
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break;
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case IPI_CALL_FUNC_SINGLE:
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generic_smp_call_function_single_interrupt();
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break;
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#ifdef CONFIG_KEXEC
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case IPI_KDUMP_CPU_STOP:
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unw_init_running(kdump_cpu_freeze, NULL);
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break;
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#endif
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default:
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printk(KERN_CRIT "Unknown IPI on CPU %d: %lu\n",
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this_cpu, which);
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break;
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}
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} while (ops);
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mb(); /* Order data access and bit testing. */
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}
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put_cpu();
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return IRQ_HANDLED;
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}
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/*
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* Called with preemption disabled.
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*/
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static inline void
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send_IPI_single (int dest_cpu, int op)
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{
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set_bit(op, &per_cpu(ipi_operation, dest_cpu));
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ia64_send_ipi(dest_cpu, IA64_IPI_VECTOR, IA64_IPI_DM_INT, 0);
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}
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/*
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* Called with preemption disabled.
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*/
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static inline void
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send_IPI_allbutself (int op)
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{
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unsigned int i;
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for_each_online_cpu(i) {
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if (i != smp_processor_id())
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send_IPI_single(i, op);
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}
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}
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/*
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* Called with preemption disabled.
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*/
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static inline void
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send_IPI_mask(const struct cpumask *mask, int op)
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{
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unsigned int cpu;
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for_each_cpu(cpu, mask) {
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send_IPI_single(cpu, op);
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}
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}
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/*
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* Called with preemption disabled.
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*/
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static inline void
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send_IPI_all (int op)
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{
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int i;
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for_each_online_cpu(i) {
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send_IPI_single(i, op);
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}
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}
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/*
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* Called with preemption disabled.
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*/
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static inline void
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send_IPI_self (int op)
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{
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send_IPI_single(smp_processor_id(), op);
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}
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#ifdef CONFIG_KEXEC
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void
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kdump_smp_send_stop(void)
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{
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send_IPI_allbutself(IPI_KDUMP_CPU_STOP);
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}
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void
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kdump_smp_send_init(void)
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{
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unsigned int cpu, self_cpu;
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self_cpu = smp_processor_id();
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for_each_online_cpu(cpu) {
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if (cpu != self_cpu) {
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if(kdump_status[cpu] == 0)
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ia64_send_ipi(cpu, 0, IA64_IPI_DM_INIT, 0);
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}
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}
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}
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#endif
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/*
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* Called with preemption disabled.
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*/
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void
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smp_send_reschedule (int cpu)
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{
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ia64_send_ipi(cpu, IA64_IPI_RESCHEDULE, IA64_IPI_DM_INT, 0);
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}
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EXPORT_SYMBOL_GPL(smp_send_reschedule);
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/*
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* Called with preemption disabled.
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*/
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static void
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smp_send_local_flush_tlb (int cpu)
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{
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ia64_send_ipi(cpu, IA64_IPI_LOCAL_TLB_FLUSH, IA64_IPI_DM_INT, 0);
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}
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void
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smp_local_flush_tlb(void)
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{
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/*
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* Use atomic ops. Otherwise, the load/increment/store sequence from
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* a "++" operation can have the line stolen between the load & store.
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* The overhead of the atomic op in negligible in this case & offers
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* significant benefit for the brief periods where lots of cpus
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* are simultaneously flushing TLBs.
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*/
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ia64_fetchadd(1, &local_tlb_flush_counts[smp_processor_id()].count, acq);
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local_flush_tlb_all();
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}
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#define FLUSH_DELAY 5 /* Usec backoff to eliminate excessive cacheline bouncing */
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void
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smp_flush_tlb_cpumask(cpumask_t xcpumask)
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{
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unsigned short *counts = __ia64_per_cpu_var(shadow_flush_counts);
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cpumask_t cpumask = xcpumask;
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int mycpu, cpu, flush_mycpu = 0;
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preempt_disable();
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mycpu = smp_processor_id();
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for_each_cpu(cpu, &cpumask)
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counts[cpu] = local_tlb_flush_counts[cpu].count & 0xffff;
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mb();
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for_each_cpu(cpu, &cpumask) {
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if (cpu == mycpu)
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flush_mycpu = 1;
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else
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smp_send_local_flush_tlb(cpu);
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}
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if (flush_mycpu)
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smp_local_flush_tlb();
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for_each_cpu(cpu, &cpumask)
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while(counts[cpu] == (local_tlb_flush_counts[cpu].count & 0xffff))
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udelay(FLUSH_DELAY);
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preempt_enable();
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}
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void
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smp_flush_tlb_all (void)
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{
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on_each_cpu((void (*)(void *))local_flush_tlb_all, NULL, 1);
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}
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void
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smp_flush_tlb_mm (struct mm_struct *mm)
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{
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cpumask_var_t cpus;
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preempt_disable();
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/* this happens for the common case of a single-threaded fork(): */
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if (likely(mm == current->active_mm && atomic_read(&mm->mm_users) == 1))
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{
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local_finish_flush_tlb_mm(mm);
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preempt_enable();
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return;
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}
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if (!alloc_cpumask_var(&cpus, GFP_ATOMIC)) {
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smp_call_function((void (*)(void *))local_finish_flush_tlb_mm,
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mm, 1);
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} else {
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cpumask_copy(cpus, mm_cpumask(mm));
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smp_call_function_many(cpus,
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(void (*)(void *))local_finish_flush_tlb_mm, mm, 1);
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free_cpumask_var(cpus);
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}
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local_irq_disable();
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local_finish_flush_tlb_mm(mm);
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local_irq_enable();
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preempt_enable();
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}
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void arch_send_call_function_single_ipi(int cpu)
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{
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send_IPI_single(cpu, IPI_CALL_FUNC_SINGLE);
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}
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void arch_send_call_function_ipi_mask(const struct cpumask *mask)
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{
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send_IPI_mask(mask, IPI_CALL_FUNC);
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}
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/*
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* this function calls the 'stop' function on all other CPUs in the system.
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*/
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void
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smp_send_stop (void)
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{
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send_IPI_allbutself(IPI_CPU_STOP);
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}
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int
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setup_profiling_timer (unsigned int multiplier)
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{
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return -EINVAL;
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}
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