On Fri, Aug 21, 2020 at 10:47:48AM +0200, Peter Zijlstra wrote: > From: Nicholas Piggin <npig...@gmail.com> > > Problem: > > raw_local_irq_save(); > local_irq_save(); > ... > local_irq_restore(); > raw_local_irq_restore(); > > existing instances: > > - lock_acquire() > raw_local_irq_save() > __lock_acquire() > arch_spin_lock(&graph_lock) > pv_wait() := kvm_wait() (same or worse for Xen/HyperV) > local_irq_save() > > - trace_clock_global() > raw_local_irq_save() > arch_spin_lock() > pv_wait() := kvm_wait() > local_irq_save() > > - apic_retrigger_irq() > raw_local_irq_save() > apic->send_IPI() := default_send_IPI_single_phys() > local_irq_save() > > Possible solutions: > > A) make it work by enabling the tracing inside raw_*() > B) make it work by keeping tracing disabled inside raw_*() > > Now, given that the only reason to use the raw_* variant is because you don't > want tracing, A) seems like a weird option (although it can be done), so we > pick B) and declare any code that ends up doing: > > raw_local_irq_save() > local_irq_save() > lockdep_assert_irqs_disabled(); > > broken. AFAICT this problem has existed forever, the only reason it came > up is because I changed IRQ tracing vs lockdep recursion and the first > instance is fairly common, the other cases hardly ever happen. >
On sparc64, this patch results in the traceback below. The traceback is gone after reverting the patch. Guenter --- [ 0.000000] WARNING: CPU: 0 PID: 0 at kernel/locking/lockdep.c:4875 check_flags.part.39+0x280/0x2a0 [ 0.000000] DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled()) [ 0.000000] Modules linked in: [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.9.0-rc3 #1 [ 0.000000] Call Trace: [ 0.000000] [<0000000000469890>] __warn+0xb0/0xe0 [ 0.000000] [<00000000004698fc>] warn_slowpath_fmt+0x3c/0x80 [ 0.000000] [<00000000004cfce0>] check_flags.part.39+0x280/0x2a0 [ 0.000000] [<00000000004cff18>] lock_acquire+0x218/0x4e0 [ 0.000000] [<0000000000d740c8>] _raw_spin_lock+0x28/0x40 [ 0.000000] [<00000000009870f4>] p1275_cmd_direct+0x14/0x60 [ 0.000000] [<00000000009872cc>] prom_getproplen+0x4c/0x60 [ 0.000000] [<0000000000987308>] prom_getproperty+0x8/0x80 [ 0.000000] [<0000000000987390>] prom_getint+0x10/0x40 [ 0.000000] [<00000000017df4b4>] prom_init+0x38/0x8c [ 0.000000] [<0000000000d6b558>] tlb_fixup_done+0x44/0x6c [ 0.000000] [<00000000ffd0e930>] 0xffd0e930 [ 0.000000] irq event stamp: 1 [ 0.000000] hardirqs last enabled at (1): [<0000000000987124>] p1275_cmd_direct+0x44/0x60 [ 0.000000] hardirqs last disabled at (0): [<0000000000000000>] 0x0 [ 0.000000] softirqs last enabled at (0): [<0000000000000000>] 0x0 [ 0.000000] softirqs last disabled at (0): [<0000000000000000>] 0x0 [ 0.000000] random: get_random_bytes called from print_oops_end_marker+0x30/0x60 with crng_init=0 [ 0.000000] ---[ end trace 0000000000000000 ]--- [ 0.000000] possible reason: unannotated irqs-off. --- bisect log: # bad: [f75aef392f869018f78cfedf3c320a6b3fcfda6b] Linux 5.9-rc3 # good: [1127b219ce9481c84edad9711626d856127d5e51] Merge tag 'fallthrough-fixes-5.9-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux git bisect start 'f75aef392f86' '1127b219ce94' # good: [8bb5021cc2ee5d5dd129a9f2f5ad2bb76eea297d] Merge tag 'powerpc-5.9-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux git bisect good 8bb5021cc2ee5d5dd129a9f2f5ad2bb76eea297d # good: [ceb2465c51195967f11f6507538579816ac67cb8] Merge tag 'irqchip-fixes-5.9-2' of git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms into irq/urgent git bisect good ceb2465c51195967f11f6507538579816ac67cb8 # bad: [b69bea8a657b681442765b06be92a2607b1bd875] Merge tag 'locking-urgent-2020-08-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip git bisect bad b69bea8a657b681442765b06be92a2607b1bd875 # good: [00b0ed2d4997af6d0a93edef820386951fd66d94] locking/lockdep: Cleanup git bisect good 00b0ed2d4997af6d0a93edef820386951fd66d94 # bad: [044d0d6de9f50192f9697583504a382347ee95ca] lockdep: Only trace IRQ edges git bisect bad 044d0d6de9f50192f9697583504a382347ee95ca # good: [021c109330ebc1f54b546c63a078ea3c31356ecb] arm64: Implement arch_irqs_disabled() git bisect good 021c109330ebc1f54b546c63a078ea3c31356ecb # good: [99dc56feb7932020502d40107a712fa302b32082] mips: Implement arch_irqs_disabled() git bisect good 99dc56feb7932020502d40107a712fa302b32082 # first bad commit: [044d0d6de9f50192f9697583504a382347ee95ca] lockdep: Only trace IRQ edges
