diff options
| author | Adrian Chadd <adrian@FreeBSD.org> | 2026-01-03 22:52:14 +0000 |
|---|---|---|
| committer | Adrian Chadd <adrian@FreeBSD.org> | 2026-01-04 02:27:48 +0000 |
| commit | 8df2e542146801fd01675e56724eaa567d04c209 (patch) | |
| tree | 5a535dc16eeb97615b2e48924b6018894afaf94e | |
| parent | 17355cf50fcbd0d8ddb638e1f2fd5861b526edbe (diff) | |
powerpc: put the isync inside the TD_LOCK() checking loop
Fix a narrow window where the lock is unlocked but the checking CPU
hasn't flushed things appropriately.
Inside this window the CPU inside cpu_switch() will loop forever thinking
the destination thread is still blocked/locked even though it is not.
This manifests as the system hanging after starting all APs.
I've seen this reliably trigger in qemu-system-ppc64 running power9 pseries
guests; the more CPUs the more likely it triggers at boot.
PR: kern/292167
Differential Revision: https://reviews.freebsd.org/D54478
Reviewed by: jhibbits
MFC after: 1 week
Relnotes: yes
| -rw-r--r-- | sys/powerpc/powerpc/swtch32.S | 2 | ||||
| -rw-r--r-- | sys/powerpc/powerpc/swtch64.S | 2 |
2 files changed, 2 insertions, 2 deletions
diff --git a/sys/powerpc/powerpc/swtch32.S b/sys/powerpc/powerpc/swtch32.S index 547e1c5a201b..ef1a397bf74d 100644 --- a/sys/powerpc/powerpc/swtch32.S +++ b/sys/powerpc/powerpc/swtch32.S @@ -141,8 +141,8 @@ cpu_switchin: blocked_loop: lwz %r7,TD_LOCK(%r2) cmpw %r6,%r7 - beq- blocked_loop isync + beq- blocked_loop #endif lwz %r17,TD_PCB(%r2) /* Get new current PCB */ diff --git a/sys/powerpc/powerpc/swtch64.S b/sys/powerpc/powerpc/swtch64.S index 5f80751c8a10..ba37274d32bb 100644 --- a/sys/powerpc/powerpc/swtch64.S +++ b/sys/powerpc/powerpc/swtch64.S @@ -194,8 +194,8 @@ cpu_switchin: blocked_loop: ld %r7,TD_LOCK(%r13) cmpd %r6,%r7 - beq- blocked_loop isync + beq- blocked_loop #endif ld %r17,TD_PCB(%r13) /* Get new PCB */ |