bisecting cause commit starting from c98ff1d013d2d53911c4b3e8ba14c7cd141cf1ed
building syzkaller on 7e2b734bac96c22086fedd1b18135da06d5e4054
testing commit c98ff1d013d2d53911c4b3e8ba14c7cd141cf1ed with gcc (GCC) 10.2.1 20210217
kernel signature: ad41b43ac0f6c9952d6b9aa45064b69ad6b5678999e8b02b8683ccbf4f0ee77a
run #0: crashed: WARNING in __percpu_ref_exit
run #1: crashed: WARNING in __percpu_ref_exit
run #2: crashed: WARNING in __percpu_ref_exit
run #3: crashed: WARNING in __percpu_ref_exit
run #4: crashed: WARNING in __percpu_ref_exit
run #5: crashed: WARNING in __percpu_ref_exit
run #6: crashed: WARNING in __percpu_ref_exit
run #7: crashed: WARNING in __percpu_ref_exit
run #8: crashed: WARNING in __percpu_ref_exit
run #9: crashed: WARNING in __percpu_ref_exit
run #10: OK
run #11: OK
run #12: OK
run #13: OK
run #14: OK
run #15: OK
run #16: OK
run #17: OK
run #18: OK
run #19: OK
testing release v5.11
testing commit f40ddce88593482919761f74910f42f4b84c004b with gcc (GCC) 10.2.1 20210217
kernel signature: ed90fbb8ff18de84ceffab28070c9539de2fa57b28f317575a02ec2d2c6a6d41
run #0: crashed: WARNING in __percpu_ref_exit
run #1: crashed: WARNING in percpu_ref_reinit
run #2: crashed: WARNING in percpu_ref_reinit
run #3: OK
run #4: OK
run #5: OK
run #6: OK
run #7: OK
run #8: OK
run #9: OK
reproducer seems to be flaky
testing release v5.10
testing commit 2c85ebc57b3e1817b6ce1a6b703928e113a90442 with gcc (GCC) 10.2.1 20210217
kernel signature: ef92a060df42786263300f4a2cafd312bd07f5ca1370e570de7b21a72c052aa1
run #0: crashed: WARNING in __percpu_ref_exit
run #1: crashed: WARNING in __percpu_ref_exit
run #2: crashed: WARNING in __percpu_ref_exit
run #3: crashed: WARNING in __percpu_ref_exit
run #4: OK
run #5: OK
run #6: OK
run #7: OK
run #8: OK
run #9: OK
run #10: OK
run #11: OK
run #12: OK
run #13: OK
run #14: OK
run #15: OK
run #16: OK
run #17: OK
run #18: OK
run #19: OK
testing release v5.9
testing commit bbf5c979011a099af5dc76498918ed7df445635b with gcc (GCC) 10.2.1 20210217
kernel signature: 4dc80a12cd84814119c6351fdb15081a2461c01ef19cac3e80fa178e7ba063cf
run #0: crashed: WARNING in percpu_ref_exit
run #1: crashed: WARNING in percpu_ref_exit
run #2: crashed: WARNING in percpu_ref_exit
run #3: crashed: WARNING in percpu_ref_exit
run #4: crashed: WARNING in percpu_ref_exit
run #5: crashed: WARNING in percpu_ref_exit
run #6: crashed: WARNING in percpu_ref_exit
run #7: crashed: WARNING in percpu_ref_exit
run #8: crashed: WARNING in percpu_ref_exit
run #9: crashed: WARNING in percpu_ref_exit
run #10: crashed: WARNING in percpu_ref_exit
run #11: OK
run #12: OK
run #13: OK
run #14: OK
run #15: OK
run #16: OK
run #17: OK
run #18: OK
run #19: OK
testing release v5.8
testing commit bcf876870b95592b52519ed4aafcf9d95999bc9c with gcc (GCC) 8.4.1 20210217
kernel signature: 3e7daf143e0ab82390ae357c3b202276d53f03d063c81d5e006eaec081b6ed42
run #0: crashed: WARNING in percpu_ref_exit
run #1: crashed: WARNING in percpu_ref_exit
run #2: crashed: WARNING in percpu_ref_exit
run #3: crashed: WARNING in percpu_ref_exit
run #4: crashed: WARNING in percpu_ref_exit
run #5: crashed: WARNING in percpu_ref_exit
run #6: crashed: WARNING in percpu_ref_exit
run #7: crashed: WARNING in percpu_ref_exit
run #8: crashed: WARNING in percpu_ref_exit
run #9: crashed: WARNING in percpu_ref_exit
run #10: crashed: WARNING in percpu_ref_exit
run #11: crashed: WARNING in percpu_ref_exit
run #12: OK
run #13: OK
run #14: OK
run #15: OK
run #16: OK
run #17: OK
run #18: OK
run #19: OK
testing release v5.7
testing commit 3d77e6a8804abcc0504c904bd6e5cdf3a5cf8162 with gcc (GCC) 8.4.1 20210217
kernel signature: c2ccfa9a08d599438cf4ad4eb97911e85a760044d8857c7fea5e2120f1753256
run #0: crashed: WARNING in percpu_ref_exit
run #1: crashed: WARNING in percpu_ref_exit
run #2: crashed: WARNING in percpu_ref_exit
run #3: crashed: WARNING in percpu_ref_exit
run #4: crashed: WARNING in percpu_ref_exit
run #5: crashed: WARNING in percpu_ref_exit
run #6: crashed: WARNING in percpu_ref_exit
run #7: crashed: WARNING in percpu_ref_exit
run #8: crashed: WARNING in percpu_ref_exit
run #9: OK
run #10: OK
run #11: OK
run #12: OK
run #13: OK
run #14: OK
run #15: OK
run #16: OK
run #17: OK
run #18: OK
run #19: OK
testing release v5.6
testing commit 7111951b8d4973bda27ff663f2cf18b663d15b48 with gcc (GCC) 8.4.1 20210217
kernel signature: 1c37951b8c55220dd6b64d36c0aaf2133892666c8681c19ebd2283c735a87012
run #0: crashed: WARNING in percpu_ref_exit
run #1: crashed: WARNING in percpu_ref_exit
run #2: crashed: WARNING in percpu_ref_exit
run #3: crashed: WARNING in percpu_ref_exit
run #4: crashed: WARNING in percpu_ref_exit
run #5: OK
run #6: OK
run #7: OK
run #8: OK
run #9: OK
run #10: OK
run #11: OK
run #12: OK
run #13: OK
run #14: OK
run #15: OK
run #16: OK
run #17: OK
run #18: OK
run #19: OK
testing release v5.5
testing commit d5226fa6dbae0569ee43ecfc08bdcd6770fc4755 with gcc (GCC) 8.4.1 20210217
kernel signature: a7917e23e2fbb3f6cbdb71eac908d2dedbee79809c65c48a9be1982423081975
all runs: OK
# git bisect start 7111951b8d4973bda27ff663f2cf18b663d15b48 d5226fa6dbae0569ee43ecfc08bdcd6770fc4755
Bisecting: 6113 revisions left to test after this (roughly 13 steps)
[9f68e3655aae6d49d6ba05dd263f99f33c2567af] Merge tag 'drm-next-2020-01-30' of git://anongit.freedesktop.org/drm/drm

testing commit 9f68e3655aae6d49d6ba05dd263f99f33c2567af with gcc (GCC) 8.4.1 20210217
kernel signature: fd31478f211a5787da7e993feb4eb912306dc3ef08710275377853a2571e3651
all runs: crashed: WARNING in percpu_ref_exit
# git bisect bad 9f68e3655aae6d49d6ba05dd263f99f33c2567af
Bisecting: 3686 revisions left to test after this (roughly 12 steps)
[fb95aae6e67c4e319a24b3eea32032d4246a5335] Merge tag 'sound-5.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound

testing commit fb95aae6e67c4e319a24b3eea32032d4246a5335 with gcc (GCC) 8.4.1 20210217
kernel signature: 3f045bb2fc88b9221f445e123748a6e6ad919ef028198243abcd6c994c78461a
all runs: OK
# git bisect good fb95aae6e67c4e319a24b3eea32032d4246a5335
Bisecting: 1843 revisions left to test after this (roughly 11 steps)
[8815a94f27d2f30fe1216ce10c7da0f6ae69ca0f] drm/vmwgfx: move the require_exist handling together

testing commit 8815a94f27d2f30fe1216ce10c7da0f6ae69ca0f with gcc (GCC) 8.4.1 20210217
kernel signature: 5ab39855b9df595c6faaa4893f5e64c1bbae42948b5cb1f5e9ca9e00fe5590d7
all runs: boot failed: general protection fault in do_mount_root
# git bisect skip 8815a94f27d2f30fe1216ce10c7da0f6ae69ca0f
Bisecting: 1842 revisions left to test after this (roughly 11 steps)
[4872e6aa217fbb475ffa0ad7bda0d9acff543f2c] drm/vmwgfx: check master authentication in surface_ref ioctls

testing commit 4872e6aa217fbb475ffa0ad7bda0d9acff543f2c with gcc (GCC) 8.4.1 20210217
kernel signature: e1f77d0882925ee7c2c24f9a73c8edb97c4b9c523f8d610f1f8bd1f4424fe7d4
all runs: boot failed: general protection fault in do_mount_root
# git bisect skip 4872e6aa217fbb475ffa0ad7bda0d9acff543f2c
Bisecting: 1842 revisions left to test after this (roughly 11 steps)
[fa889d85551e0bd962fdefe1cc113f9ba1d04a36] Merge tag 'gpio-v5.6-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio

testing commit fa889d85551e0bd962fdefe1cc113f9ba1d04a36 with gcc (GCC) 8.4.1 20210217
kernel signature: fb26ad3dbd211ece740adc5d364cdf8c6089ceadf8bde0767bf6388fa8b5ec9b
all runs: OK
# git bisect good fa889d85551e0bd962fdefe1cc113f9ba1d04a36
Bisecting: 1827 revisions left to test after this (roughly 11 steps)
[dd22dfa62c9cb2669ed4b181e359645108c69578] Merge branch 'linux-5.6' of git://github.com/skeggsb/linux into drm-next

testing commit dd22dfa62c9cb2669ed4b181e359645108c69578 with gcc (GCC) 8.4.1 20210217
kernel signature: 5adb17bbf19e72f13642834c715becc617542edc4e59d704e557906f14e091c0
all runs: boot failed: general protection fault in do_mount_root
# git bisect skip dd22dfa62c9cb2669ed4b181e359645108c69578
Bisecting: 1827 revisions left to test after this (roughly 11 steps)
[1d47d0bb72895e754ffbdc410314ddb9c790c6fa] fbdev: omapfb: use devm_platform_ioremap_resource() to simplify code

testing commit 1d47d0bb72895e754ffbdc410314ddb9c790c6fa with gcc (GCC) 8.4.1 20210217
kernel signature: 503055328a21f254f3c40113c44a677f830714c9d32e4de874b965b16a17075e
all runs: OK
# git bisect good 1d47d0bb72895e754ffbdc410314ddb9c790c6fa
Bisecting: 1573 revisions left to test after this (roughly 11 steps)
[3d4743131b8de970faa4b979ead0fadfe5d2de9d] Backmerge v5.5-rc7 into drm-next

testing commit 3d4743131b8de970faa4b979ead0fadfe5d2de9d with gcc (GCC) 8.4.1 20210217
kernel signature: 7494a1012ab5d34d9d6e4a174c6691ece8e2278b03703a17e585925c9721e163
all runs: OK
# git bisect good 3d4743131b8de970faa4b979ead0fadfe5d2de9d
Bisecting: 751 revisions left to test after this (roughly 10 steps)
[7ba31c3f2f1ee095d8126f4d3757fc3b2bc3c838] Merge tag 'staging-5.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging

testing commit 7ba31c3f2f1ee095d8126f4d3757fc3b2bc3c838 with gcc (GCC) 8.4.1 20210217
kernel signature: 854a9394ad22395732f9ec8866fe526afe66893e4a0e7b14b326e9672599e5a2
run #0: boot failed: can't ssh into the instance
run #1: OK
run #2: OK
run #3: OK
run #4: OK
run #5: OK
run #6: OK
run #7: OK
run #8: OK
run #9: OK
run #10: OK
run #11: OK
run #12: OK
run #13: OK
run #14: OK
run #15: OK
run #16: OK
run #17: OK
run #18: OK
run #19: OK
# git bisect good 7ba31c3f2f1ee095d8126f4d3757fc3b2bc3c838
Bisecting: 303 revisions left to test after this (roughly 9 steps)
[33c84e89abe4a92ab699c33029bd54269d574782] Merge tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi

testing commit 33c84e89abe4a92ab699c33029bd54269d574782 with gcc (GCC) 8.4.1 20210217
kernel signature: a1c2ff81398ca6c06635fe544e52d5ba5a0c68faca5c3f30f5ff376dd4e8a8eb
all runs: OK
# git bisect good 33c84e89abe4a92ab699c33029bd54269d574782
Bisecting: 119 revisions left to test after this (roughly 7 steps)
[893e591b59036f9bc629f55bce715d67bdd266a2] Merge tag 'devicetree-for-5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux

testing commit 893e591b59036f9bc629f55bce715d67bdd266a2 with gcc (GCC) 8.4.1 20210217
kernel signature: 6bba9405f5adfcda14058ea5074bd30d2a616bb358773f8bb687878842817e87
all runs: crashed: WARNING in percpu_ref_exit
# git bisect bad 893e591b59036f9bc629f55bce715d67bdd266a2
Bisecting: 95 revisions left to test after this (roughly 7 steps)
[9ca4c6429f92598a84e4c3292ea7d187c9d7b033] Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc

testing commit 9ca4c6429f92598a84e4c3292ea7d187c9d7b033 with gcc (GCC) 8.4.1 20210217
kernel signature: 227e52c5523dedcf5970c2937d23882f80df12819d1fd010290d910c4dcd6123
run #0: crashed: WARNING in percpu_ref_exit
run #1: crashed: WARNING in percpu_ref_exit
run #2: crashed: WARNING in percpu_ref_exit
run #3: crashed: WARNING in percpu_ref_exit
run #4: crashed: WARNING in percpu_ref_exit
run #5: crashed: WARNING in percpu_ref_exit
run #6: crashed: WARNING in percpu_ref_exit
run #7: crashed: WARNING in percpu_ref_exit
run #8: crashed: WARNING in percpu_ref_exit
run #9: crashed: WARNING in percpu_ref_exit
run #10: crashed: WARNING in percpu_ref_exit
run #11: crashed: WARNING in percpu_ref_exit
run #12: crashed: WARNING in percpu_ref_exit
run #13: crashed: WARNING in percpu_ref_exit
run #14: crashed: WARNING in percpu_ref_exit
run #15: crashed: WARNING in percpu_ref_exit
run #16: crashed: WARNING in percpu_ref_exit
run #17: crashed: WARNING in percpu_ref_exit
run #18: crashed: WARNING in percpu_ref_exit
run #19: OK
# git bisect bad 9ca4c6429f92598a84e4c3292ea7d187c9d7b033
Bisecting: 43 revisions left to test after this (roughly 6 steps)
[66f4af93da5761d2fa05c0dc673a47003cdb9cfe] io_uring: add support for probing opcodes

testing commit 66f4af93da5761d2fa05c0dc673a47003cdb9cfe with gcc (GCC) 8.4.1 20210217
kernel signature: 0fa79c2b477cc4d676d7bd685d18def6a6011f7d49d1a76a6a064695c531936b
all runs: OK
# git bisect good 66f4af93da5761d2fa05c0dc673a47003cdb9cfe
Bisecting: 21 revisions left to test after this (roughly 5 steps)
[3e4827b05d2ac2d377ed136a52829ec46787bf4b] io_uring: add support for epoll_ctl(2)

testing commit 3e4827b05d2ac2d377ed136a52829ec46787bf4b with gcc (GCC) 8.4.1 20210217
kernel signature: 4ae8183a4bb259478e2c5a6d0a7fc0f5b9cf7d563a484f0f8c84f42e16201817
all runs: crashed: WARNING in percpu_ref_exit
# git bisect bad 3e4827b05d2ac2d377ed136a52829ec46787bf4b
Bisecting: 10 revisions left to test after this (roughly 4 steps)
[8cdf2193a3335b4cfb6e023b41ac293d0843d287] io_uring: add comment for drain_next

testing commit 8cdf2193a3335b4cfb6e023b41ac293d0843d287 with gcc (GCC) 8.4.1 20210217
kernel signature: a0c190291f11d015617f842284abbcc32a0198c19e649b9d768505cb962d15a9
all runs: OK
# git bisect good 8cdf2193a3335b4cfb6e023b41ac293d0843d287
Bisecting: 4 revisions left to test after this (roughly 3 steps)
[071698e13ac6ba786dfa22349a7b62deb5a9464d] io_uring: allow registering credentials

testing commit 071698e13ac6ba786dfa22349a7b62deb5a9464d with gcc (GCC) 8.4.1 20210217
kernel signature: 5b398ffdfa821a730ef747399fd88c6e73e6b80765c2f04ea72087be2637413a
all runs: crashed: WARNING in percpu_ref_exit
# git bisect bad 071698e13ac6ba786dfa22349a7b62deb5a9464d
Bisecting: 2 revisions left to test after this (roughly 2 steps)
[cccf0ee834559ae0b327b40290e14f6a2a017177] io_uring/io-wq: don't use static creds/mm assignments

testing commit cccf0ee834559ae0b327b40290e14f6a2a017177 with gcc (GCC) 8.4.1 20210217
kernel signature: b6864d24faa9cf32c95648cf3f53091e3051cc97c07dc669d02c9d9351b58b91
all runs: OK
# git bisect good cccf0ee834559ae0b327b40290e14f6a2a017177
Bisecting: 0 revisions left to test after this (roughly 1 step)
[24369c2e3bb06d8c4e71fd6ceaf4f8a01ae79b7c] io_uring: add io-wq workqueue sharing

testing commit 24369c2e3bb06d8c4e71fd6ceaf4f8a01ae79b7c with gcc (GCC) 8.4.1 20210217
kernel signature: 2dabc8135a32af138f38782289cde1ff4f35134fa6c926393b41c839bc3ced94
all runs: crashed: WARNING in percpu_ref_exit
# git bisect bad 24369c2e3bb06d8c4e71fd6ceaf4f8a01ae79b7c
Bisecting: 0 revisions left to test after this (roughly 0 steps)
[eba6f5a330cf042bb0001f0b5e8cbf21be1b25d6] io-wq: allow grabbing existing io-wq

Reproducer flagged being flaky
revisions tested: 26, total time: 8h3m25.540936892s (build: 2h58m17.38791094s, test: 5h0m46.051140592s)
error: bisection is taking too long (>8h0m0s), aborting