Segfault when num_threads is set on certain CPU #2114
Description
What happened?
The following segfault error emits when the FrankenPHP powered Docker image is up:
php-1 | {"level":"info","ts":1767878883.108642,"msg":"maxprocs: Leaving GOMAXPROCS=24: CPU quota undefined"}
php-1 | {"level":"info","ts":1767878883.108994,"msg":"GOMEMLIMIT is updated","package":"github.com/KimMachineGun/automemlimit/memlimit","GOMEMLIMIT":60257824358,"previous":9223372036854775807}
php-1 | {"level":"info","ts":1767878883.1102464,"msg":"using config from file","file":"/etc/caddy/Caddyfile"}
php-1 | {"level":"error","ts":1767878883.110694,"msg":"Setting the \"transport_url\" directive is not available anymore, use the \"transport\" directive instead"}
php-1 | {"level":"info","ts":1767878883.111232,"msg":"adapted config to JSON","adapter":"caddyfile"}
php-1 | {"level":"warn","ts":1767878883.1112518,"msg":"Caddyfile input is not formatted; run 'caddy fmt --overwrite' to fix inconsistencies","adapter":"caddyfile","file":"/etc/caddy/Caddyfile","line":21}
php-1 | {"level":"info","ts":1767878883.1220682,"logger":"admin","msg":"admin endpoint started","address":"localhost:2019","enforce_origin":false,"origins":["//[::1]:2019","//127.0.0.1:2019","//localhost:2019"]}
php-1 | {"level":"info","ts":1767878883.1222134,"logger":"http.auto_https","msg":"automatic HTTPS is completely disabled for server","server_name":"srv0"}
php-1 | {"level":"info","ts":1767878883.1224532,"logger":"http.auto_https","msg":"automatic HTTPS is completely disabled for server","server_name":"srv1"}
php-1 | {"level":"info","ts":1767878883.122822,"logger":"tls.cache.maintenance","msg":"started background certificate maintenance","cache":"0xc000466c00"}
php-1 | {"level":"debug","ts":1767878883.1230936,"logger":"http.auto_https","msg":"adjusted config","tls":{"automation":{"policies":[{}]}},"http":{"servers":{"srv0":{"listen":[":2020"],"routes":[{"handle":[{"handler":"metrics"}]}],"automatic_https":{"disable":true}},"srv1":{"listen":[":80"],"routes":[{"handle":[{"handler":"vars","root":"/app/public"},{"handler":"headers","response":{"require":{"headers":{"Permissions-Policy":null}},"set":{"Permissions-Policy":["browsing-topics=()"]}}},{"encodings":{"gzip":{},"zstd":{}},"handler":"encode","prefer":["zstd","gzip"]},{"anonymous":true,"dispatch_timeout":10000000000,"handler":"mercure","publisher_jwt":{"alg":"{env.MERCURE_PUBLISHER_JWT_ALG}","key":"{env.MERCURE_PUBLISHER_JWT_KEY}"},"subscriber_jwt":{"alg":"{env.MERCURE_SUBSCRIBER_JWT_ALG}","key":"{env.MERCURE_SUBSCRIBER_JWT_KEY}"},"subscriptions":true,"write_timeout":0},{"handler":"vulcain"}]},{"handle":[{"handler":"static_response","headers":{"Location":["{http.request.orig_uri.path}/"]},"status_code":308}]},{"handle":[{"handler":"rewrite","uri":"{http.matchers.file.relative}"}]},{"handle":[{"handler":"php","split_path":[".php"]}]},{"handle":[{"handler":"file_server"}]}],"automatic_https":{"disable":true},"logs":{"default_logger_name":"log0"}}},"metrics":{}}}
php-1 | {"level":"debug","ts":1767878883.1265736,"logger":"frankenphp","msg":"shutting down autoscaling","autoScaledThreads":0}
php-1 | {"level":"info","ts":1767878883.1266198,"msg":"maxprocs: No GOMAXPROCS change to reset"}
php-1 | panic: runtime error: invalid memory address or nil pointer dereference
php-1 | [signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x17cf876]
php-1 |
php-1 | goroutine 1 [running]:
php-1 | github.com/dunglas/frankenphp.drainPHPThreads()
php-1 | /go/src/app/phpmainthread.go:84 +0x36
php-1 | github.com/dunglas/frankenphp.Shutdown()
php-1 | /go/src/app/frankenphp.go:368 +0x75
php-1 | github.com/dunglas/frankenphp.Init({0xc0001572d0, 0x8, 0x12?})
php-1 | /go/src/app/frankenphp.go:281 +0x4cd
php-1 | github.com/dunglas/frankenphp/caddy.(*FrankenPHPApp).Start(0xc000964600)
php-1 | /go/src/app/caddy/app.go:168 +0xbe7
php-1 | github.com/caddyserver/caddy/v2.run.func2(...)
php-1 | /root/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.10.2/caddy.go:438
php-1 | github.com/caddyserver/caddy/v2.run(0xc00045d5d8?, 0x1)
php-1 | /root/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.10.2/caddy.go:454 +0x434
php-1 | github.com/caddyserver/caddy/v2.unsyncedDecodeAndRun({0xc000435800, 0x7a3, 0x800}, 0x1)
php-1 | /root/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.10.2/caddy.go:347 +0x145
php-1 | github.com/caddyserver/caddy/v2.changeConfig({0x1e851ad, 0x4}, {0x1e8b062, 0x7}, {0xc000435000, 0x7a3, 0x800}, {0x0, 0x0}, 0x1)
php-1 | /root/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.10.2/caddy.go:238 +0x6a5
php-1 | github.com/caddyserver/caddy/v2.Load({0xc000435000, 0x7a3, 0x800}, 0x1)
php-1 | /root/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.10.2/caddy.go:137 +0x22d
php-1 | github.com/caddyserver/caddy/v2/cmd.cmdRun({0x0?})
php-1 | /root/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.10.2/cmd/commandfuncs.go:240 +0x80d
php-1 | github.com/caddyserver/caddy/v2/cmd.init.1.func2.WrapCommandFuncForCobra.1(0xc00096a308, {0x1e85229?, 0x4?, 0x1e851e1?})
php-1 | /root/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.10.2/cmd/cobra.go:141 +0x2f
php-1 | github.com/spf13/cobra.(*Command).execute(0xc00096a308, {0xc000126fc0, 0x2, 0x2})
php-1 | /root/go/pkg/mod/github.com/spf13/cobra@v1.10.2/command.go:1015 +0xb02
php-1 | github.com/spf13/cobra.(*Command).ExecuteC(0xc0001f5b08)
php-1 | /root/go/pkg/mod/github.com/spf13/cobra@v1.10.2/command.go:1148 +0x465
php-1 | github.com/spf13/cobra.(*Command).Execute(...)
php-1 | /root/go/pkg/mod/github.com/spf13/cobra@v1.10.2/command.go:1071
php-1 | github.com/caddyserver/caddy/v2/cmd.Main()
php-1 | /root/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.10.2/cmd/main.go:72 +0x65
php-1 | main.main()
php-1 | /go/src/app/caddy/frankenphp/main.go:15 +0xf
This only happens when I run the production image on my dev machine, but not on the production server, so it took me some time to figure out why. Turns out this is caused by a Caddy configuration I added earlier:
frankenphp {
num_threads 32
}
Which, for some unknown reason, doesn't play well on my dev machine. I am running Docker Desktop on Windows, but here is the lscpu output on WSL anyway:
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Address sizes: 48 bits physical, 48 bits virtual
Byte Order: Little Endian
CPU(s): 24
On-line CPU(s) list: 0-23
Vendor ID: AuthenticAMD
Model name: AMD Ryzen 9 7900 12-Core Processor
CPU family: 25
Model: 97
Thread(s) per core: 2
Core(s) per socket: 12
Socket(s): 1
Stepping: 2
BogoMIPS: 7399.83
Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good
nopl tsc_reliable nonstop_tsc cpuid extd_apicid pni pclmulqdq ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm cmp_legacy svm cr8_
legacy abm sse4a misalignsse 3dnowprefetch osvw topoext perfctr_core ssbd ibrs ibpb stibp vmmcall fsgsbase bmi1 avx2 smep bmi2 erms invpcid avx512f avx512dq rdseed adx
smap avx512ifma clflushopt clwb avx512cd sha_ni avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves avx512_bf16 clzero xsaveerptr arat npt nrip_save tsc_scale vmcb_clean f
lushbyasid decodeassists pausefilter pfthreshold v_vmsave_vmload avx512vbmi umip avx512_vbmi2 gfni vaes vpclmulqdq avx512_vnni avx512_bitalg avx512_vpopcntdq rdpid fsrm
I tried setting num_threads to 16, 24, 32, 48, but all failed. I have to remove the num_threads statement in order to have FrankenPHP running.
Build Type
Docker (Debian Trixie)
Worker Mode
No
Operating System
GNU/Linux
CPU Architecture
x86_64
PHP configuration
N/A