idpf: properly handle XDP program unloading during system reboot #28
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alobakin
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Aug 4, 2025
Without the change `perf `hangs up on charaster devices. On my system
it's enough to run system-wide sampler for a few seconds to get the
hangup:
$ perf record -a -g --call-graph=dwarf
$ perf report
# hung
`strace` shows that hangup happens on reading on a character device
`/dev/dri/renderD128`
$ strace -y -f -p 2780484
strace: Process 2780484 attached
pread64(101</dev/dri/renderD128>, strace: Process 2780484 detached
It's call trace descends into `elfutils`:
$ gdb -p 2780484
(gdb) bt
#0 0x00007f5e508f04b7 in __libc_pread64 (fd=101, buf=0x7fff9df7edb0, count=0, offset=0)
at ../sysdeps/unix/sysv/linux/pread64.c:25
#1 0x00007f5e52b79515 in read_file () from /<<NIX>>/elfutils-0.192/lib/libelf.so.1
#2 0x00007f5e52b25666 in libdw_open_elf () from /<<NIX>>/elfutils-0.192/lib/libdw.so.1
#3 0x00007f5e52b25907 in __libdw_open_file () from /<<NIX>>/elfutils-0.192/lib/libdw.so.1
#4 0x00007f5e52b120a9 in dwfl_report_elf@@ELFUTILS_0.156 ()
from /<<NIX>>/elfutils-0.192/lib/libdw.so.1
#5 0x000000000068bf20 in __report_module (al=al@entry=0x7fff9df80010, ip=ip@entry=139803237033216, ui=ui@entry=0x5369b5e0)
at util/dso.h:537
#6 0x000000000068c3d1 in report_module (ip=139803237033216, ui=0x5369b5e0) at util/unwind-libdw.c:114
#7 frame_callback (state=0x535aef10, arg=0x5369b5e0) at util/unwind-libdw.c:242
#8 0x00007f5e52b261d3 in dwfl_thread_getframes () from /<<NIX>>/elfutils-0.192/lib/libdw.so.1
#9 0x00007f5e52b25bdb in get_one_thread_cb () from /<<NIX>>/elfutils-0.192/lib/libdw.so.1
#10 0x00007f5e52b25faa in dwfl_getthreads () from /<<NIX>>/elfutils-0.192/lib/libdw.so.1
#11 0x00007f5e52b26514 in dwfl_getthread_frames () from /<<NIX>>/elfutils-0.192/lib/libdw.so.1
#12 0x000000000068c6ce in unwind__get_entries (cb=cb@entry=0x5d4620 <unwind_entry>, arg=arg@entry=0x10cd5fa0,
thread=thread@entry=0x1076a290, data=data@entry=0x7fff9df80540, max_stack=max_stack@entry=127,
best_effort=best_effort@entry=false) at util/thread.h:152
#13 0x00000000005dae95 in thread__resolve_callchain_unwind (evsel=0x106006d0, thread=0x1076a290, cursor=0x10cd5fa0,
sample=0x7fff9df80540, max_stack=127, symbols=true) at util/machine.c:2939
#14 thread__resolve_callchain_unwind (thread=0x1076a290, cursor=0x10cd5fa0, evsel=0x106006d0, sample=0x7fff9df80540,
max_stack=127, symbols=true) at util/machine.c:2920
#15 __thread__resolve_callchain (thread=0x1076a290, cursor=0x10cd5fa0, evsel=0x106006d0, evsel@entry=0x7fff9df80440,
sample=0x7fff9df80540, parent=parent@entry=0x7fff9df804a0, root_al=root_al@entry=0x7fff9df80440, max_stack=127, symbols=true)
at util/machine.c:2970
#16 0x00000000005d0cb2 in thread__resolve_callchain (thread=<optimized out>, cursor=<optimized out>, evsel=0x7fff9df80440,
sample=<optimized out>, parent=0x7fff9df804a0, root_al=0x7fff9df80440, max_stack=127) at util/machine.h:198
#17 sample__resolve_callchain (sample=<optimized out>, cursor=<optimized out>, parent=parent@entry=0x7fff9df804a0,
evsel=evsel@entry=0x106006d0, al=al@entry=0x7fff9df80440, max_stack=max_stack@entry=127) at util/callchain.c:1127
#18 0x0000000000617e08 in hist_entry_iter__add (iter=iter@entry=0x7fff9df80480, al=al@entry=0x7fff9df80440, max_stack_depth=127,
arg=arg@entry=0x7fff9df81ae0) at util/hist.c:1255
#19 0x000000000045d2d0 in process_sample_event (tool=0x7fff9df81ae0, event=<optimized out>, sample=0x7fff9df80540,
evsel=0x106006d0, machine=<optimized out>) at builtin-report.c:334
#20 0x00000000005e3bb1 in perf_session__deliver_event (session=0x105ff2c0, event=0x7f5c7d735ca0, tool=0x7fff9df81ae0,
file_offset=2914716832, file_path=0x105ffbf0 "perf.data") at util/session.c:1367
#21 0x00000000005e8d93 in do_flush (oe=0x105ffa50, show_progress=false) at util/ordered-events.c:245
#22 __ordered_events__flush (oe=0x105ffa50, how=OE_FLUSH__ROUND, timestamp=<optimized out>) at util/ordered-events.c:324
#23 0x00000000005e1f64 in perf_session__process_user_event (session=0x105ff2c0, event=0x7f5c7d752b18, file_offset=2914835224,
file_path=0x105ffbf0 "perf.data") at util/session.c:1419
#24 0x00000000005e47c7 in reader__read_event (rd=rd@entry=0x7fff9df81260, session=session@entry=0x105ff2c0,
--Type <RET> for more, q to quit, c to continue without paging--
quit
prog=prog@entry=0x7fff9df81220) at util/session.c:2132
#25 0x00000000005e4b37 in reader__process_events (rd=0x7fff9df81260, session=0x105ff2c0, prog=0x7fff9df81220)
at util/session.c:2181
#26 __perf_session__process_events (session=0x105ff2c0) at util/session.c:2226
#27 perf_session__process_events (session=session@entry=0x105ff2c0) at util/session.c:2390
#28 0x0000000000460add in __cmd_report (rep=0x7fff9df81ae0) at builtin-report.c:1076
torvalds#29 cmd_report (argc=<optimized out>, argv=<optimized out>) at builtin-report.c:1827
torvalds#30 0x00000000004c5a40 in run_builtin (p=p@entry=0xd8f7f8 <commands+312>, argc=argc@entry=1, argv=argv@entry=0x7fff9df844b0)
at perf.c:351
torvalds#31 0x00000000004c5d63 in handle_internal_command (argc=argc@entry=1, argv=argv@entry=0x7fff9df844b0) at perf.c:404
torvalds#32 0x0000000000442de3 in run_argv (argcp=<synthetic pointer>, argv=<synthetic pointer>) at perf.c:448
torvalds#33 main (argc=<optimized out>, argv=0x7fff9df844b0) at perf.c:556
The hangup happens because nothing in` perf` or `elfutils` checks if a
mapped file is easily readable.
The change conservatively skips all non-regular files.
Signed-off-by: Sergei Trofimovich <[email protected]>
Acked-by: Namhyung Kim <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Namhyung Kim <[email protected]>
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During a system reboot, the
pci_device_shutdown()function is invoked before the network device is unregistered. However, the XDP program is unloaded as part of the netdev unregistration process—by which point most of the device's features have already been stopped.Previously, the
IDPF_REMOVE_IN_PROGflag was used to detect device removal and handle XDP unloading early. However, this flag does not cover the netdev unregistration path during shutdown.This patch improves detection of shutdown or module removal scenarios by checking both
IDPF_REMOVE_IN_PROGandIDPF_VPORT_REG_NETDEVflags. This ensures the XDP program is unloaded early and cleanly, avoiding unnecessary system reconfiguration.