Back in April, I posted an RFC patch set to help mitigate a common issue where a timer gets armed just before it is freed, and when the timer goes off, it crashes in the timer code without any evidence of who the culprit was. I got side tracked and never finished up on that patch set. Since this type of crash is still our #1 crash we are seeing in the field, it has become a priority again to finish it.
This is v3 of that patch set. Thomas Gleixner posted an untested version that makes timer->function NULL as the flag that it is shutdown. I took that code, tested it (fixed it up), added more comments, and changed the name to timer_shutdown_sync(). I also converted it to use WARN_ON_ONCE() instead of just WARN_ON() as Linus asked for.
I then created a trivial coccinelle script to find where del_timer*() is called before being freed, and converted them all to timer_shutdown*() (There was a couple that still used del_timer() instead of del_timer_sync()).
I also updated DEBUG_OBJECTS_TIMERS to check from where the timer is ever armed, to calling of timer_shutdown_sync(), and it will trigger if a timer is freed in between. The current way is to only check if the timer is armed, but that means it only triggers if the race condition is hit, and with experience, it's not run on enough machines to catch all of them. By triggering it from the time the timer is armed to the time it is shutdown, it catches all potential cases even if the race condition is not hit.
I went though the result of the cocinelle script, and updated the locations. Some locations were caught by DEBUG_OBJECTS_TIMERS as the coccinelle script only checked for timers being freed in the same function as the del_timer*().
Ideally, I would have the first patch go into this rc cycle, which is mostly non functional as it will allow the other patches to come in via the respective subsystems in the next merge window.
Changes since v2: https://lore.kernel.org/all/20221027150525.753064657@goodmis.org/
- Talking with Thomas Gleixner, he wanted a better name space and to remove the "del_" portion of the API.
- Since there's now a shutdown interface that does not synchronize, to keep it closer to del_timer() and del_timer_sync(), the API is now:
timer_shutdown() - same as del_timer() but deactivates the timer.
timer_shutdown_sync() - same as del_timer_sync() but deactivates the timer.
- Added a few more locations that got converted.
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git trace/timers
Head SHA1: 25106f0bb7968b3e8c746a7853f44b51840746c3
Steven Rostedt (Google) (33): timers: Add timer_shutdown_sync() and timer_shutdown() to be called before freeing timers timers: s390/cmm: Use timer_shutdown_sync() before freeing timer timers: sh: Use timer_shutdown_sync() before freeing timer timers: block: Use timer_shutdown_sync() before freeing timer timers: ACPI: Use timer_shutdown_sync() before freeing timer timers: atm: Use timer_shutdown_sync() before freeing timer timers: PM: Use timer_shutdown_sync() timers: Bluetooth: Use timer_shutdown_sync() before freeing timer timers: hangcheck: Use timer_shutdown_sync() before freeing timer timers: ipmi: Use timer_shutdown_sync() before freeing timer random: use timer_shutdown_sync() before freeing timer timers: dma-buf: Use timer_shutdown_sync() before freeing timer timers: drm: Use timer_shutdown_sync() before freeing timer timers: HID: Use timer_shutdown_sync() before freeing timer timers: Input: Use timer_shutdown_sync() before freeing timer timers: mISDN: Use timer_shutdown_sync() before freeing timer timers: leds: Use timer_shutdown_sync() before freeing timer timers: media: Use timer_shutdown_sync() before freeing timer timers: net: Use timer_shutdown_sync() before freeing timer timers: usb: Use timer_shutdown_sync() before freeing timer timers: cgroup: Use timer_shutdown_sync() before freeing timer timers: workqueue: Use timer_shutdown_sync() before freeing timer timers: nfc: pn533: Use timer_shutdown_sync() before freeing timer timers: pcmcia: Use timer_shutdown_sync() before freeing timer timers: scsi: Use timer_shutdown_sync() and timer_shutdown() before freeing timer timers: tty: Use timer_shutdown_sync() before freeing timer timers: ext4: Use timer_shutdown_sync() before freeing timer timers: fs/nilfs2: Use timer_shutdown_sync() before freeing timer timers: ALSA: Use timer_shutdown_sync() before freeing timer timers: jbd2: Use timer_shutdown() before freeing timer timers: sched/psi: Use timer_shutdown_sync() before freeing timer timers: x86/mce: Use __init_timer() for resetting timers timers: Expand DEBUG_OBJECTS_TIMER to check if it ever was used
---- .../RCU/Design/Requirements/Requirements.rst | 2 +- Documentation/core-api/local_ops.rst | 2 +- Documentation/kernel-hacking/locking.rst | 5 + arch/s390/mm/cmm.c | 4 +- arch/sh/drivers/push-switch.c | 2 +- arch/x86/kernel/cpu/mce/core.c | 14 ++- block/blk-iocost.c | 2 +- block/blk-iolatency.c | 2 +- block/blk-stat.c | 2 +- block/blk-throttle.c | 2 +- block/kyber-iosched.c | 2 +- drivers/acpi/apei/ghes.c | 2 +- drivers/atm/idt77105.c | 4 +- drivers/atm/idt77252.c | 4 +- drivers/atm/iphase.c | 2 +- drivers/base/power/wakeup.c | 7 +- drivers/block/drbd/drbd_main.c | 2 +- drivers/block/loop.c | 2 +- drivers/block/sunvdc.c | 2 +- drivers/bluetooth/hci_bcsp.c | 2 +- drivers/bluetooth/hci_h5.c | 2 +- drivers/bluetooth/hci_qca.c | 4 +- drivers/char/hangcheck-timer.c | 4 +- drivers/char/ipmi/ipmi_msghandler.c | 2 +- drivers/char/ipmi/ipmi_ssif.c | 4 +- drivers/char/random.c | 2 +- drivers/dma-buf/st-dma-fence.c | 2 +- drivers/gpu/drm/gud/gud_pipe.c | 2 +- drivers/gpu/drm/i915/i915_sw_fence.c | 2 +- drivers/hid/hid-wiimote-core.c | 2 +- drivers/input/keyboard/locomokbd.c | 2 +- drivers/input/keyboard/omap-keypad.c | 2 +- drivers/input/mouse/alps.c | 2 +- drivers/input/serio/hil_mlc.c | 2 +- drivers/input/serio/hp_sdc.c | 2 +- drivers/isdn/hardware/mISDN/hfcmulti.c | 6 +- drivers/isdn/mISDN/l1oip_core.c | 4 +- drivers/isdn/mISDN/timerdev.c | 4 +- drivers/leds/trigger/ledtrig-activity.c | 2 +- drivers/leds/trigger/ledtrig-heartbeat.c | 2 +- drivers/leds/trigger/ledtrig-pattern.c | 2 +- drivers/leds/trigger/ledtrig-transient.c | 2 +- drivers/media/pci/ivtv/ivtv-driver.c | 2 +- drivers/media/usb/pvrusb2/pvrusb2-hdw.c | 18 ++-- drivers/media/usb/s2255/s2255drv.c | 4 +- drivers/net/ethernet/intel/i40e/i40e_main.c | 6 +- drivers/net/ethernet/marvell/sky2.c | 2 +- drivers/net/ethernet/sun/sunvnet.c | 2 +- drivers/net/usb/sierra_net.c | 2 +- drivers/net/wireless/intel/iwlwifi/iwl-dbg-tlv.c | 2 +- drivers/net/wireless/intersil/hostap/hostap_ap.c | 2 +- drivers/net/wireless/marvell/mwifiex/main.c | 2 +- drivers/net/wireless/microchip/wilc1000/hif.c | 8 +- drivers/nfc/pn533/pn533.c | 2 +- drivers/nfc/pn533/uart.c | 2 +- drivers/pcmcia/bcm63xx_pcmcia.c | 2 +- drivers/pcmcia/electra_cf.c | 2 +- drivers/pcmcia/omap_cf.c | 2 +- drivers/pcmcia/pd6729.c | 4 +- drivers/pcmcia/yenta_socket.c | 4 +- drivers/scsi/qla2xxx/qla_edif.c | 4 +- drivers/scsi/scsi_lib.c | 1 + drivers/staging/media/atomisp/i2c/atomisp-lm3554.c | 2 +- drivers/tty/n_gsm.c | 2 +- drivers/tty/sysrq.c | 2 +- drivers/usb/gadget/udc/m66592-udc.c | 2 +- drivers/usb/serial/garmin_gps.c | 2 +- drivers/usb/serial/mos7840.c | 2 +- fs/ext4/super.c | 2 +- fs/jbd2/journal.c | 2 + fs/nilfs2/segment.c | 2 +- include/linux/timer.h | 100 +++++++++++++++++-- include/linux/workqueue.h | 4 +- kernel/cgroup/cgroup.c | 2 +- kernel/sched/psi.c | 1 + kernel/time/timer.c | 106 ++++++++++++++------- kernel/workqueue.c | 4 +- net/802/garp.c | 2 +- net/802/mrp.c | 2 +- net/bridge/br_multicast.c | 6 +- net/bridge/br_multicast_eht.c | 4 +- net/core/gen_estimator.c | 2 +- net/core/neighbour.c | 2 + net/ipv4/inet_connection_sock.c | 2 +- net/ipv4/inet_timewait_sock.c | 3 +- net/ipv4/ipmr.c | 2 +- net/ipv6/ip6mr.c | 2 +- net/mac80211/mesh_pathtbl.c | 2 +- net/netfilter/ipset/ip_set_list_set.c | 2 +- net/netfilter/ipvs/ip_vs_lblc.c | 2 +- net/netfilter/ipvs/ip_vs_lblcr.c | 2 +- net/netfilter/xt_LED.c | 2 +- net/rxrpc/conn_object.c | 2 +- net/sched/cls_flow.c | 2 +- net/sunrpc/svc.c | 2 +- net/sunrpc/xprt.c | 2 +- net/tipc/discover.c | 2 +- net/tipc/monitor.c | 2 +- sound/i2c/other/ak4117.c | 2 +- sound/synth/emux/emux.c | 2 +- 100 files changed, 310 insertions(+), 175 deletions(-)