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31b265b3ba
linux/kernel
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Douglas Anderson 31b265b3ba tracing: kdb: Fix ftdump to not sleep 
As reported back in 2016-11 [1], the "ftdump" kdb command triggers a
BUG for "sleeping function called from invalid context".

kdb's "ftdump" command wants to call ring_buffer_read_prepare() in
atomic context.  A very simple solution for this is to add allocation
flags to ring_buffer_read_prepare() so kdb can call it without
triggering the allocation error.  This patch does that.

Note that in the original email thread about this, it was suggested
that perhaps the solution for kdb was to either preallocate the buffer
ahead of time or create our own iterator.  I'm hoping that this
alternative of adding allocation flags to ring_buffer_read_prepare()
can be considered since it means I don't need to duplicate more of the
core trace code into "trace_kdb.c" (for either creating my own
iterator or re-preparing a ring allocator whose memory was already
allocated).

NOTE: another option for kdb is to actually figure out how to make it
reuse the existing ftrace_dump() function and totally eliminate the
duplication.  This sounds very appealing and actually works (the "sr
z" command can be seen to properly dump the ftrace buffer).  The
downside here is that ftrace_dump() fully consumes the trace buffer.
Unless that is changed I'd rather not use it because it means "ftdump
| grep xyz" won't be very useful to search the ftrace buffer since it
will throw away the whole trace on the first grep.  A future patch to
dump only the last few lines of the buffer will also be hard to
implement.

[1] https://lkml.kernel.org/r/20161117191605.GA21459@google.com

Link: http://lkml.kernel.org/r/20190308193205.213659-1-dianders@chromium.org

Reported-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2019-03-13 09:46:10 -04:00
..
bpf bpf: fix inner map masking to prevent oob under speculation 2019-01-18 15:19:56 -08:00
cgroup Merge branch 'for-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2018-12-29 10:57:20 -08:00
configs kvm_config: add CONFIG_VIRTIO_MENU 2018-10-24 20:55:56 -04:00
debug kdb: use bool for binary state indicators 2018-12-30 08:31:52 +00:00
dma swiotlb: clear io_tlb_start and io_tlb_end in swiotlb_exit 2019-01-16 09:59:17 -05:00
events uprobes: convert uprobe.ref to refcount_t 2019-02-15 13:10:14 -05:00
gcov
irq genirq/irqdesc: Fix double increment in alloc_descs() 2019-01-18 00:43:09 +01:00
livepatch livepatch: Replace synchronize_sched() with synchronize_rcu() 2018-12-01 12:38:50 -08:00
locking locking/rwsem: Fix (possible) missed wakeup 2019-01-21 11:15:39 +01:00
power mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00
printk Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
rcu rcutorture: Don't do busted forward-progress testing 2018-12-01 12:45:42 -08:00
sched Merge branch 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-02-03 09:02:03 -08:00
time posix-cpu-timers: Unbreak timer rearming 2019-01-15 16:34:37 +01:00
trace tracing: kdb: Fix ftdump to not sleep 2019-03-13 09:46:10 -04:00
.gitignore
acct.c
async.c
audit_fsnotify.c audit: minimize our use of audit_log_format() 2018-11-26 18:40:00 -05:00
audit_tree.c audit: minimize our use of audit_log_format() 2018-11-26 18:40:00 -05:00
audit_watch.c audit: minimize our use of audit_log_format() 2018-11-26 18:40:00 -05:00
audit.c audit: remove duplicated include from audit.c 2018-12-14 12:09:30 -05:00
audit.h audit: use current whenever possible 2018-11-26 18:41:21 -05:00
auditfilter.c
auditsc.c audit: use current whenever possible 2018-11-26 18:41:21 -05:00
backtracetest.c
bounds.c kbuild: fix kernel/bounds.c 'W=1' warning 2018-10-31 08:54:14 -07:00
capability.c
compat.c make 'user_access_begin()' do 'access_ok()' 2019-01-04 12:56:09 -08:00
configs.c
context_tracking.c
cpu_pm.c
cpu.c cpu/hotplug: Fix "SMT disabled by BIOS" detection for KVM 2019-01-30 19:27:00 +01:00
crash_core.c kernel/crash_core.c: print timestamp using time64_t 2018-08-22 10:52:47 -07:00
crash_dump.c
cred.c cred: export get_task_cred(). 2018-12-19 13:52:44 -05:00
delayacct.c delayacct: track delays from thrashing cache pages 2018-10-26 16:26:32 -07:00
dma.c
elfcore.c
exec_domain.c
exit.c kernel/exit.c: release ptraced tasks before zap_pid_ns_processes 2019-02-01 15:46:23 -08:00
extable.c
fail_function.c kernel/fail_function.c: remove meaningless null pointer check before debugfs_remove_recursive 2018-10-31 08:54:12 -07:00
fork.c Merge branch 'akpm' (patches from Andrew) 2019-01-08 18:58:29 -08:00
freezer.c PM / reboot: Eliminate race between reboot and suspend 2018-08-06 12:35:20 +02:00
futex.c futex: Fix (possible) missed wakeup 2019-01-21 11:15:38 +01:00
groups.c
hung_task.c kernel/hung_task.c: break RCU locks based on jiffies 2019-01-04 13:13:45 -08:00
iomem.c
irq_work.c
jump_label.c jump_label: move 'asm goto' support test to Kconfig 2019-01-06 09:46:51 +09:00
kallsyms.c kallsyms: reduce size a little on 64-bit 2018-09-10 22:54:33 +09:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt kconfig: warn no new line at end of file 2018-12-15 17:44:35 +09:00
kcov.c kernel/kcov.c: mark write_comp_data() as notrace 2019-01-04 13:13:47 -08:00
kexec_core.c mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00
kexec_file.c kexec_file: kexec_walk_memblock() only walks a dedicated region at kdump 2018-12-06 14:38:50 +00:00
kexec_internal.h
kexec.c kexec: add call to LSM hook in original kexec_load syscall 2018-07-16 12:31:57 -07:00
kmod.c
kprobes.c Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-26 14:45:18 -08:00
ksysfs.c
kthread.c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-08-13 11:25:07 -07:00
latencytop.c
Makefile kbuild: change filechk to surround the given command with { } 2019-01-06 09:46:51 +09:00
memremap.c mm/hmm: fix memremap.h, move dev_page_fault_t callback to hmm 2018-12-28 12:11:52 -08:00
module_signing.c modsign: use all trusted keys to verify module signature 2018-11-07 14:41:41 +01:00
module-internal.h
module.c jump_label: move 'asm goto' support test to Kconfig 2019-01-06 09:46:51 +09:00
notifier.c
nsproxy.c
padata.c padata: clean an indentation issue, remove extraneous space 2018-11-16 14:11:04 +08:00
panic.c kernel/sysctl: add panic_print into sysctl 2019-01-04 13:13:47 -08:00
params.c
pid_namespace.c signal: Use group_send_sig_info to kill all processes in a pid namespace 2018-09-16 16:08:25 +02:00
pid.c Fix failure path in alloc_pid() 2018-12-28 12:42:30 -08:00
profile.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
ptrace.c Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
range.c
reboot.c kernel/reboot.c: export pm_power_off_prepare 2018-09-11 16:13:24 +01:00
relay.c
resource.c kernel, resource: check for IORESOURCE_SYSRAM in release_mem_region_adjustable 2018-12-28 12:11:49 -08:00
rseq.c Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
seccomp.c seccomp: fix UAF in user-trap code 2019-01-15 09:43:12 -08:00
signal.c Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
smp.c cpu/hotplug: Fix "SMT disabled by BIOS" detection for KVM 2019-01-30 19:27:00 +01:00
smpboot.c smpboot: Remove cpumask from the API 2018-07-03 09:20:44 +02:00
smpboot.h
softirq.c Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-10-25 11:43:47 -07:00
stackleak.c stackleak: Mark stackleak_track_stack() as notrace 2018-12-05 19:31:44 -08:00
stacktrace.c
stop_machine.c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-08-13 11:25:07 -07:00
sys_ni.c y2038: socket: Add compat_sys_recvmmsg_time64 2018-12-18 16:13:04 +01:00
sys.c kernel/sys.c: Clarify that UNAME26 does not generate unique versions anymore 2019-01-14 10:38:03 +12:00
sysctl_binary.c kernel/sysctl: add panic_print into sysctl 2019-01-04 13:13:47 -08:00
sysctl.c kernel/sysctl: add panic_print into sysctl 2019-01-04 13:13:47 -08:00
task_work.c
taskstats.c
test_kprobes.c
torture.c torture: Remove unnecessary "ret" variables 2018-12-01 12:45:35 -08:00
tracepoint.c tracing: Replace synchronize_sched() and call_rcu_sched() 2018-11-27 09:21:41 -08:00
tsacct.c
ucount.c
uid16.c
uid16.h
umh.c umh: add exit routine for UMH process 2019-01-11 18:05:40 -08:00
up.c smp,cpumask: introduce on_each_cpu_cond_mask 2018-10-09 16:51:11 +02:00
user_namespace.c userns: also map extents in the reverse map to kernel IDs 2018-11-07 23:51:16 -06:00
user-return-notifier.c
user.c userns: use irqsave variant of refcount_dec_and_lock() 2018-08-22 10:52:47 -07:00
utsname_sysctl.c sys: don't hold uts_sem while accessing userspace memory 2018-08-11 02:05:53 -05:00
utsname.c
watchdog_hld.c watchdog: Mark watchdog touch functions as notrace 2018-08-30 12:56:40 +02:00
watchdog.c watchdog: Mark watchdog touch functions as notrace 2018-08-30 12:56:40 +02:00
workqueue_internal.h psi: fix aggregation idle shut-off 2019-02-01 15:46:23 -08:00
workqueue.c psi: fix aggregation idle shut-off 2019-02-01 15:46:23 -08:00