diff options
author | Nicholas Piggin <npiggin@gmail.com> | 2018-04-25 04:17:53 +0200 |
---|---|---|
committer | Michael Ellerman <mpe@ellerman.id.au> | 2018-04-25 12:38:08 +0200 |
commit | ac61c1156623455c46701654abd8c99720bceea1 (patch) | |
tree | c7f94e67f672b815fc5815d3f4ce7af623359f3e /arch/powerpc | |
parent | rtc: opal: Fix OPAL RTC driver OPAL_BUSY loops (diff) | |
download | linux-ac61c1156623455c46701654abd8c99720bceea1.tar.xz linux-ac61c1156623455c46701654abd8c99720bceea1.zip |
powerpc: Fix smp_send_stop NMI IPI handling
The NMI IPI handler for a receiving CPU increments nmi_ipi_busy_count
over the handler function call, which causes later smp_send_nmi_ipi()
callers to spin until the call is finished.
The stop_this_cpu() function never returns, so the busy count is never
decremeted, which can cause the system to hang in some cases. For
example panic() will call smp_send_stop() early on which calls
stop_this_cpu() on other CPUs, then later in the reboot path,
pnv_restart() will call smp_send_stop() again, which hangs.
Fix this by adding a special case to the stop_this_cpu() handler to
decrement the busy count, because it will never return.
Now that the NMI/non-NMI versions of stop_this_cpu() are different,
split them out into separate functions rather than doing #ifdef tricks
to share the body between the two functions.
Fixes: 6bed3237624e3 ("powerpc: use NMI IPI for smp_send_stop")
Reported-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Split out the functions, tweak change log a bit]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc')
-rw-r--r-- | arch/powerpc/kernel/smp.c | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c index e16ec7b3b427..3582f30b60b7 100644 --- a/arch/powerpc/kernel/smp.c +++ b/arch/powerpc/kernel/smp.c @@ -565,11 +565,7 @@ void crash_send_ipi(void (*crash_ipi_callback)(struct pt_regs *)) } #endif -#ifdef CONFIG_NMI_IPI -static void stop_this_cpu(struct pt_regs *regs) -#else static void stop_this_cpu(void *dummy) -#endif { /* Remove this CPU */ set_cpu_online(smp_processor_id(), false); @@ -580,10 +576,26 @@ static void stop_this_cpu(void *dummy) spin_cpu_relax(); } +#ifdef CONFIG_NMI_IPI +static void nmi_stop_this_cpu(struct pt_regs *regs) +{ + /* + * This is a special case because it never returns, so the NMI IPI + * handling would never mark it as done, which makes any later + * smp_send_nmi_ipi() call spin forever. Mark it done now. + */ + nmi_ipi_lock(); + nmi_ipi_busy_count--; + nmi_ipi_unlock(); + + stop_this_cpu(NULL); +} +#endif + void smp_send_stop(void) { #ifdef CONFIG_NMI_IPI - smp_send_nmi_ipi(NMI_IPI_ALL_OTHERS, stop_this_cpu, 1000000); + smp_send_nmi_ipi(NMI_IPI_ALL_OTHERS, nmi_stop_this_cpu, 1000000); #else smp_call_function(stop_this_cpu, NULL, 0); #endif |