Will Deacon 0821295b23 asm-generic/mmiowb: Allow mmiowb_set_pending() when preemptible() ... [ Upstream commit bd024e82e4 ] Although mmiowb() is concerned only with serialising MMIO writes occuring in contexts where a spinlock is held, the call to mmiowb_set_pending() from the MMIO write accessors can occur in preemptible contexts, such as during driver probe() functions where ordering between CPUs is not usually a concern, assuming that the task migration path provides the necessary ordering guarantees. Unfortunately, the default implementation of mmiowb_set_pending() is not preempt-safe, as it makes use of a a per-cpu variable to track its internal state. This has been reported to generate the following splat on riscv: | BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1 | caller is regmap_mmio_write32le+0x1c/0x46 | CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.8.0-rc3-hfu+ #1 | Call Trace: | walk_stackframe+0x0/0x7a | dump_stack+0x6e/0x88 | regmap_mmio_write32le+0x18/0x46 | check_preemption_disabled+0xa4/0xaa | regmap_mmio_write32le+0x18/0x46 | regmap_mmio_write+0x26/0x44 | regmap_write+0x28/0x48 | sifive_gpio_probe+0xc0/0x1da Although it's possible to fix the driver in this case, other splats have been seen from other drivers, including the infamous 8250 UART, and so it's better to address this problem in the mmiowb core itself. Fix mmiowb_set_pending() by using the raw_cpu_ptr() to get at the mmiowb state and then only updating the 'mmiowb_pending' field if we are not preemptible (i.e. we have a non-zero nesting count). Cc: Arnd Bergmann <arnd@arndb.de> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Guo Ren <guoren@kernel.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Reported-by: Palmer Dabbelt <palmer@dabbelt.com> Reported-by: Emil Renner Berthing <kernel@esmil.dk> Tested-by: Emil Renner Berthing <kernel@esmil.dk> Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com> Acked-by: Palmer Dabbelt <palmerdabbelt@google.com> Link: https://lore.kernel.org/r/20200716112816.7356-1-will@kernel.org Signed-off-by: Will Deacon <will@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		2020-07-29 10:18:40 +02:00
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acpi	…
asm-generic	asm-generic/mmiowb: Allow mmiowb_set_pending() when preemptible()	2020-07-29 10:18:40 +02:00
clocksource	…
crypto	crypto: af_alg - fix use-after-free in af_alg_accept() due to bh_lock_sock()	2020-07-09 09:37:52 +02:00
drm	…
dt-bindings	…
keys	…
kvm	…
linux	Input: add `SW_MACHINE_COVER`	2020-07-29 10:18:36 +02:00
math-emu	…
media	…
misc	…
net	sched: consistently handle layer3 header accesses in the presence of VLANs	2020-07-22 09:32:48 +02:00
pcmcia	…
ras	…
rdma	RDMA/core: Fix double destruction of uobject	2020-06-03 08:21:25 +02:00
scsi	…
soc	…
sound	ALSA: compress: fix partial_drain completion state	2020-07-16 08:16:39 +02:00
target	…
trace	rxrpc: Fix trace string	2020-07-22 09:33:17 +02:00
uapi	Input: add `SW_MACHINE_COVER`	2020-07-29 10:18:36 +02:00
vdso	…
video	…
xen	…