freebsd-dev/sys/kern
Kirk McKusick bbb1e07d65 Peter Holm reports that his test that does an umount(8) on an active
mount point while numerous tests are running that are writing to
files on that mount point cause the unmount(8) to hang forever.

The unmount(8) system call is handled in the kernel by the dounmount()
function. The cause of the hang is that prior to dounmount() calling
VFS_UNMOUNT() it is calling VFS_SYNC(mp, MNT_WAIT). The MNT_WAIT
flag indicates that VFS_SYNC() should not return until all the dirty
buffers associated with the mount point have been written to disk.
Because user processes are allowed to continue writing and can do
so faster than the data can be written to disk, the call to VFS_SYNC()
can never finish.

Unlike VFS_SYNC(), the VFS_UNMOUNT() routine can suspend all processes
when they request to do a write thus having a finite number of dirty
buffers to write that cannot be expanded. There is no need to call
VFS_SYNC() before calling VFS_UNMOUNT(), because VFS_UNMOUNT() needs
to flush everything again anyway after suspending writes, to catch
anything that was dirtied between the VFS_SYNC() and writes being
suspended.

The fix is to simply remove the unnecessary call to VFS_SYNC() from
dounmount().

Reported by:  Peter Holm
Analysis by:  Chuck Silvers
Tested by:    Peter Holm
MFC after:    7 days
Sponsored by: Netflix
2020-01-15 18:53:32 +00:00
..
bus_if.m Add necessary bits for Linux KPI to work correctly on powerpc 2019-08-04 19:28:10 +00:00
capabilities.conf Add a shm_open2 syscall to support upcoming memfd_create 2019-09-25 17:59:15 +00:00
clock_if.m
cpufreq_if.m
device_if.m
genassym.sh
genoffset.c Merge td_epochnest with td_no_sleeping. 2019-10-29 17:28:25 +00:00
genoffset.sh expose thread_lite definition to tied modules 2018-07-03 02:50:07 +00:00
imgact_aout.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
imgact_binmisc.c Add helper functions to copy strings into struct image_args. 2018-11-29 21:00:56 +00:00
imgact_elf32.c
imgact_elf64.c
imgact_elf.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
imgact_shell.c Add helper functions to copy strings into struct image_args. 2018-11-29 21:00:56 +00:00
init_main.c random(9): Deprecate random(9), remove meaningless srandom(9) 2019-12-26 19:41:09 +00:00
init_sysent.c Jail and capability mode for shm_rename; add audit support for shm_rename 2019-11-18 13:31:16 +00:00
kern_acct.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
kern_alq.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
kern_clock.c sleep(9), sleepqueue(9): const'ify wchan pointers 2019-12-24 16:19:33 +00:00
kern_clocksource.c Rename hardclock_cnt() to hardclock() and remove the old implementation. 2018-09-06 02:10:59 +00:00
kern_condvar.c
kern_conf.c devfs: introduce a per-dev lock to protect ->si_devsw 2019-11-30 16:46:19 +00:00
kern_cons.c kern_cons: add a stub kbdinit for configs with no keyboard/console drivers 2019-12-26 15:47:19 +00:00
kern_context.c Remove superfluous bzero in getcontext/swapcontext/sendsig 2018-11-26 20:56:05 +00:00
kern_cpu.c kern_cpu: When adding abs frequency allow for unordered insertion 2018-07-19 11:28:14 +00:00
kern_cpuset.c bitset: rename confusing macro NAND to ANDNOT 2019-12-13 09:32:16 +00:00
kern_ctf.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
kern_descrip.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
kern_dtrace.c
kern_dump.c [PPC64] Initial kernel minidump implementation 2019-10-14 13:04:04 +00:00
kern_environment.c Follow up r352244: kenv: tighten up assertions 2019-09-12 14:34:46 +00:00
kern_et.c
kern_event.c Avoid relying on header pollution from sys/refcount.h. 2019-07-29 20:26:01 +00:00
kern_exec.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
kern_exit.c procdesc: allow to collect status through wait(1) if process is traced 2019-11-25 18:33:21 +00:00
kern_fail.c Use callout(9) instead of deprecated timeout(9) for fail points. 2019-12-13 19:26:04 +00:00
kern_ffclock.c
kern_fork.c schedlock 1/4 2019-12-15 21:11:15 +00:00
kern_hhook.c
kern_idle.c
kern_intr.c schedlock 4/4 2019-12-15 21:26:50 +00:00
kern_jail.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
kern_kcov.c Change synchonization rules for vm_page reference counting. 2019-09-09 21:32:42 +00:00
kern_khelp.c
kern_kthread.c schedlock 1/4 2019-12-15 21:11:15 +00:00
kern_ktr.c Add KERNEL_PANICKED macro for use in place of direct panicstr tests 2020-01-12 06:07:54 +00:00
kern_ktrace.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
kern_linker.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
kern_lock.c Add KERNEL_PANICKED macro for use in place of direct panicstr tests 2020-01-12 06:07:54 +00:00
kern_lockf.c vfs: introduce v_irflag and make v_type smaller 2019-12-08 21:30:04 +00:00
kern_lockstat.c Add lockmgr(9) probes to the lockstat DTrace provider. 2019-08-21 23:43:58 +00:00
kern_loginclass.c Replace hand-rolled unrefs if > 1 with refcount_release_if_not_last 2018-12-07 16:11:45 +00:00
kern_malloc.c Change malloc_domain() to return the allocation size to the caller. 2020-01-09 15:02:48 +00:00
kern_mbuf.c Use a separate lock for the zone and keg. This provides concurrency 2020-01-04 03:15:34 +00:00
kern_mib.c Create a new sysctl subtree, machdep.mitigations. Its purpose is to organize 2019-11-15 23:27:17 +00:00
kern_module.c
kern_mtxpool.c Mark mtxpool_sleep as read mostly, not frequently. 2020-01-05 12:46:35 +00:00
kern_mutex.c Add KERNEL_PANICKED macro for use in place of direct panicstr tests 2020-01-12 06:07:54 +00:00
kern_ntptime.c Clear pad bytes in the struct exported by kern.ntp_pll.gettime. 2018-11-20 20:32:10 +00:00
kern_osd.c
kern_physio.c Allocate pager bufs from UMA instead of 80-ish mutex protected linked list. 2019-01-15 01:02:16 +00:00
kern_pmc.c Add malloc_domainset(9) and _domainset variants to other allocator KPIs. 2018-10-30 18:26:34 +00:00
kern_poll.c schedlock 4/4 2019-12-15 21:26:50 +00:00
kern_priv.c Check for probes enabled in priv_check_cred before evaluting the error. 2018-12-19 23:28:29 +00:00
kern_proc.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
kern_procctl.c Add procctl(PROC_STACKGAP_CTL) 2019-09-03 18:56:25 +00:00
kern_prot.c malloc: remove assumptions about MINALLOCSIZE 2020-01-14 02:14:02 +00:00
kern_racct.c proc: eliminate the zombproc list 2019-08-28 16:18:23 +00:00
kern_rangelock.c rangelock: add rangelock_cookie_assert 2019-09-15 02:59:53 +00:00
kern_rctl.c
kern_resource.c dd kern_getpriority(), make Linuxulator use it. 2020-01-12 14:25:44 +00:00
kern_rmlock.c Plug a warning in read-mostly spinlocks reported by gcc. 2019-12-27 13:37:19 +00:00
kern_rwlock.c locks: add default delay struct 2020-01-05 12:48:19 +00:00
kern_sdt.c
kern_sema.c
kern_sendfile.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
kern_sharedpage.c Fix the last few cases that grab without busy or valid. The grab functions must 2019-12-02 22:38:25 +00:00
kern_shutdown.c Add "panicked" boolean which can be tested instead of panicstr 2020-01-12 06:09:10 +00:00
kern_sig.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
kern_switch.c Add KERNEL_PANICKED macro for use in place of direct panicstr tests 2020-01-12 06:07:54 +00:00
kern_sx.c locks: add default delay struct 2020-01-05 12:48:19 +00:00
kern_synch.c Add KERNEL_PANICKED macro for use in place of direct panicstr tests 2020-01-12 06:07:54 +00:00
kern_syscalls.c add a sanity check to the system call registration code 2019-12-11 15:52:29 +00:00
kern_sysctl.c kern_sysctl: make sysctl.debug work as intended 2020-01-06 19:47:59 +00:00
kern_tc.c Initialize timehands linkage much earlier. 2019-09-09 12:42:48 +00:00
kern_thr.c schedlock 1/4 2019-12-15 21:11:15 +00:00
kern_thread.c vfs: prealloc vnodes in getnewvnode_reserve 2020-01-11 22:58:14 +00:00
kern_time.c Disallow excessively small times of day in clock_settime(2). 2019-05-03 21:26:44 +00:00
kern_timeout.c Remove the deprecated timeout(9) interface. 2019-12-13 21:03:12 +00:00
kern_tslog.c
kern_ubsan.c Teach the kernel KUBSAN runtime about alignment_assumption 2019-05-28 09:12:15 +00:00
kern_umtx.c Rename umtxq_check_susp() to thread_check_susp() 2020-01-02 22:13:59 +00:00
kern_uuid.c Use sbuf_cat() in GEOM confxml generation. 2019-06-19 15:36:02 +00:00
kern_xxx.c Normalize COMPAT_43 syscall declarations. 2018-12-04 16:48:47 +00:00
ksched.c
link_elf_obj.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
link_elf.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
linker_if.m
Make.tags.inc Remove a couple of harmless stray references to nandfs. 2019-06-25 16:39:25 +00:00
Makefile Set .ORDER for makesyscalls generated files 2020-01-10 18:24:17 +00:00
makesyscalls.sh Restore the ability to set capenabled directly in syscalls.conf. 2019-09-30 20:58:29 +00:00
md4c.c
md5c.c
msi_if.m
p1003_1b.c
pic_if.m
posix4_mib.c
sched_4bsd.c Add KERNEL_PANICKED macro for use in place of direct panicstr tests 2020-01-12 06:07:54 +00:00
sched_ule.c Add KERNEL_PANICKED macro for use in place of direct panicstr tests 2020-01-12 06:07:54 +00:00
serdev_if.m
stack_protector.c Revert r346292 (permit_nonrandom_stackcookies) 2019-05-13 23:37:44 +00:00
subr_acl_nfs4.c Remove unused argument to priv_check_cred. 2018-12-11 19:32:16 +00:00
subr_acl_posix1e.c Remove unused argument to priv_check_cred. 2018-12-11 19:32:16 +00:00
subr_atomic64.c emulated atomic64: disable interrupts as the lock mechanism on !SMP 2020-01-03 18:29:20 +00:00
subr_autoconf.c
subr_blist.c Simplify the processing a leaf mask to find big-enough ranges of set 2019-12-14 19:44:42 +00:00
subr_boot.c When parsing command line stuff, treat tabs and spaces the same. 2019-04-18 22:52:12 +00:00
subr_bufring.c
subr_bus_dma.c Add an external mbuf buffer type that holds multiple unmapped pages. 2019-06-29 00:48:33 +00:00
subr_bus.c malloc: remove assumptions about MINALLOCSIZE 2020-01-14 02:14:02 +00:00
subr_busdma_bufalloc.c Add malloc_domainset(9) and _domainset variants to other allocator KPIs. 2018-10-30 18:26:34 +00:00
subr_capability.c
subr_clock.c Kill tz_minuteswest and tz_dsttime. 2019-03-12 04:49:47 +00:00
subr_compressor.c GZIO: Update to use zlib 1.2.11. 2019-08-25 07:50:44 +00:00
subr_counter.c Fix pre-SI_SUB_CPU initialization of per-CPU counters. 2018-07-10 00:18:12 +00:00
subr_coverage.c Extract the coverage sanitizer KPI to a new file. 2019-01-29 11:04:17 +00:00
subr_csan.c Add KERNEL_PANICKED macro for use in place of direct panicstr tests 2020-01-12 06:07:54 +00:00
subr_devmap.c Print upper 32 bits in devmap table entries 2019-12-20 03:40:53 +00:00
subr_devstat.c Use atomic for start_count in devstat_start_transaction(). 2019-12-30 03:13:38 +00:00
subr_disk.c Fix botched merge with 355066 2019-03-12 05:10:41 +00:00
subr_dummy_vdso_tc.c
subr_early.c Add a file missed in r339321 2018-10-12 00:32:45 +00:00
subr_epoch.c Code must not unlock a mutex while owning the thread lock. 2020-01-13 14:30:19 +00:00
subr_eventhandler.c Include ktr.h in more compilation units 2019-05-21 20:38:48 +00:00
subr_fattime.c
subr_filter.c This commit adds BBR (Bottleneck Bandwidth and RTT) congestion control. This 2019-09-24 18:18:11 +00:00
subr_firmware.c Factor out check for mounted root file system. 2019-11-28 08:47:36 +00:00
subr_gtaskqueue.c schedlock 1/4 2019-12-15 21:11:15 +00:00
subr_hash.c
subr_hints.c res_find: Fix fallback logic 2018-08-18 19:45:56 +00:00
subr_intr.c Extract eventfilter declarations to sys/_eventfilter.h 2019-05-20 00:38:23 +00:00
subr_kdb.c bitset: rename confusing macro NAND to ANDNOT 2019-12-13 09:32:16 +00:00
subr_kobj.c Prevent some kobj memory allocation failures from panicking the system. 2019-01-31 22:27:39 +00:00
subr_lock.c locks: add default delay struct 2020-01-05 12:48:19 +00:00
subr_log.c
subr_mchain.c
subr_module.c Have preload_delete_name() free pages backing preloaded data. 2018-07-19 20:00:28 +00:00
subr_msgbuf.c msgbuf: Light detailing (const'ify and bool'itize) 2018-08-09 17:42:27 +00:00
subr_param.c riscv: restore default HZ=1000, keep QEMU at HZ=100 2019-09-07 05:13:31 +00:00
subr_pcpu.c schedlock 1/4 2019-12-15 21:11:15 +00:00
subr_pctrie.c kern/subr_pctrie: Fix mismatched signedness in assertion comparison 2019-04-06 21:56:24 +00:00
subr_pidctrl.c
subr_power.c Extract eventfilter declarations to sys/_eventfilter.h 2019-05-20 00:38:23 +00:00
subr_prf.c Add KERNEL_PANICKED macro for use in place of direct panicstr tests 2020-01-12 06:07:54 +00:00
subr_prof.c
subr_rangeset.c Implement rangesets. 2019-02-20 09:38:19 +00:00
subr_rman.c add support for marking interrupt handlers as suspended 2018-12-17 17:11:00 +00:00
subr_rtc.c Improve error messages from clock_if.m method failures. 2018-09-02 20:17:51 +00:00
subr_sbuf.c sbuf(9): Add sbuf_nl_terminate() API 2019-08-07 19:27:14 +00:00
subr_scanf.c Add support for 'j', 't' and 'z' flags to kernel sscanf(). 2019-08-16 19:46:22 +00:00
subr_sfbuf.c
subr_sglist.c Add an external mbuf buffer type that holds multiple unmapped pages. 2019-06-29 00:48:33 +00:00
subr_sleepqueue.c sleep(9), sleepqueue(9): const'ify wchan pointers 2019-12-24 16:19:33 +00:00
subr_smp.c Add KERNEL_PANICKED macro for use in place of direct panicstr tests 2020-01-12 06:07:54 +00:00
subr_stack.c Add debugging facility EPOCH_TRACE that checks that epochs entered are 2019-09-25 18:26:31 +00:00
subr_stats.c random(9): Deprecate random(9), remove meaningless srandom(9) 2019-12-26 19:41:09 +00:00
subr_syscall.c Don't pass error from syscallenter() to syscallret(). 2019-07-15 21:25:16 +00:00
subr_taskqueue.c schedlock 1/4 2019-12-15 21:11:15 +00:00
subr_terminal.c kernel terminal should initialize fg and bg variables before calling TUNABLE_INT_FETCH 2019-09-26 07:19:26 +00:00
subr_trap.c vfs: prealloc vnodes in getnewvnode_reserve 2020-01-11 22:58:14 +00:00
subr_turnstile.c schedlock 4/4 2019-12-15 21:26:50 +00:00
subr_uio.c
subr_unit.c kern/subr_unit: Rip srandomdev, random(3) out of dead code 2019-12-13 04:48:20 +00:00
subr_vmem.c Use a precise bit count for the slab free items in UMA. This significantly 2019-12-02 22:44:34 +00:00
subr_witness.c Add KERNEL_PANICKED macro for use in place of direct panicstr tests 2020-01-12 06:07:54 +00:00
sys_capability.c Let kern.trap_enotcap be set as a tunable. 2018-12-06 17:29:37 +00:00
sys_generic.c posix_fallocate: push vnop implementation into the fileop layer 2020-01-08 19:05:32 +00:00
sys_getrandom.c Fix a typo in r356667 comment 2020-01-12 23:52:16 +00:00
sys_pipe.c Fix handling of PIPE_EOF in the direct write path. 2019-11-11 20:44:30 +00:00
sys_procdesc.c procdesc: allow to collect status through wait(1) if process is traced 2019-11-25 18:33:21 +00:00
sys_process.c Define macro VM_MAP_ENTRY_FOREACH for enumerating the entries in a vm_map. 2019-10-08 07:14:21 +00:00
sys_socket.c
syscalls.c sysent: regenerate after r352747. 2019-09-26 15:41:10 +00:00
syscalls.master Jail and capability mode for shm_rename; add audit support for shm_rename 2019-11-18 13:31:16 +00:00
systrace_args.c sysent: regenerate after r354835 2019-11-18 23:31:12 +00:00
sysv_ipc.c sysv: get rid of fork/exit hooks if the code is compiled in 2019-05-04 19:05:30 +00:00
sysv_msg.c
sysv_sem.c
sysv_shm.c Simplify anonymous memory handling with an OBJ_ANON flag. This eliminates 2019-11-19 23:19:43 +00:00
tty_compat.c
tty_info.c Add KERNEL_PANICKED macro for use in place of direct panicstr tests 2020-01-12 06:07:54 +00:00
tty_inq.c
tty_outq.c
tty_pts.c tty_pts: don't rely on tty header pollution for sys/mutex.h 2019-11-29 03:56:01 +00:00
tty_tty.c Extract eventfilter declarations to sys/_eventfilter.h 2019-05-20 00:38:23 +00:00
tty_ttydisc.c Replace ttyprintf with sbuf_printf and tty drain routine 2018-10-20 18:31:36 +00:00
tty.c vfs: introduce v_irflag and make v_type smaller 2019-12-08 21:30:04 +00:00
uipc_accf.c
uipc_debug.c
uipc_domain.c - Move global network epoch definition to epoch.h, as more different 2020-01-15 03:34:21 +00:00
uipc_ktls.c Since this code uses if_ref()/if_rele() it must include if_var.h 2020-01-15 03:39:11 +00:00
uipc_mbuf2.c m_pulldown(): Change an if () panic() into a KASSERT(). 2019-11-06 22:40:19 +00:00
uipc_mbuf.c kTLS: Fix a bug where we would not encrypt anon data inplace. 2019-09-27 20:08:19 +00:00
uipc_mbufhash.c
uipc_mqueue.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
uipc_sem.c Remove unused argument to priv_check_cred. 2018-12-11 19:32:16 +00:00
uipc_shm.c shmfd: posix_fallocate(2): only take rangelock for section we need 2020-01-09 04:03:17 +00:00
uipc_sockbuf.c sysctl: hide 2.x era compat node 2020-01-02 01:23:43 +00:00
uipc_socket.c Cleanup unneeded includes that crept in with r353292. 2019-10-09 16:59:42 +00:00
uipc_syscalls.c Only enable COMPAT_43 changes for syscalls ABI for a.out processes. 2019-08-11 19:16:07 +00:00
uipc_usrreq.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
vfs_acl.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
vfs_aio.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
vfs_bio.c Add KERNEL_PANICKED macro for use in place of direct panicstr tests 2020-01-12 06:07:54 +00:00
vfs_cache.c vfs: incomplete pass at converting more ints to u_long 2020-01-11 22:56:20 +00:00
vfs_cluster.c Do not use waitable allocation of pbuf when creating cluster for write. 2019-12-23 20:15:19 +00:00
vfs_default.c vfs: in vop_stdadd_writecount only vlazy vnodes on mounts using msync 2020-01-15 01:34:05 +00:00
vfs_export.c Ensure that directory entry padding bytes are zeroed. 2018-11-23 22:24:59 +00:00
vfs_extattr.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
vfs_hash.c vfs: incomplete pass at converting more ints to u_long 2020-01-11 22:56:20 +00:00
vfs_init.c vfs: add optional root vnode caching 2019-10-06 22:14:32 +00:00
vfs_lookup.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
vfs_mount.c Peter Holm reports that his test that does an umount(8) on an active 2020-01-15 18:53:32 +00:00
vfs_mountroot.c vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00
vfs_subr.c vfs: per-cpu batched requeuing of free vnodes 2020-01-13 02:39:41 +00:00
vfs_syscalls.c posix_fallocate: push vnop implementation into the fileop layer 2020-01-08 19:05:32 +00:00
vfs_vnops.c posix_fallocate: push vnop implementation into the fileop layer 2020-01-08 19:05:32 +00:00
vnode_if.src vfs: drop the mostly unused flags argument from VOP_UNLOCK 2020-01-03 22:29:58 +00:00