| Message ID | 20220718192844.1805158-9-yury.norov@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Introduce DEBUG_BITMAP config option and bitmap_check_params() | expand |
On Mon, Jul 18, 2022 at 12:28:36PM -0700, Yury Norov wrote: > --- > kernel/smp.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/kernel/smp.c b/kernel/smp.c > index 7ed2b9b12f74..f96fdf944b4a 100644 > --- a/kernel/smp.c > +++ b/kernel/smp.c > @@ -942,7 +942,11 @@ static void smp_call_function_many_cond(const struct cpumask *mask, > > if (run_remote) { > cfd = this_cpu_ptr(&cfd_data); > - cpumask_and(cfd->cpumask, mask, cpu_online_mask); > + if (mask == cpu_online_mask) > + cpumask_copy(cfd->cpumask, cpu_online_mask); > + else > + cpumask_and(cfd->cpumask, mask, cpu_online_mask); > + Or... you could optimize cpumask_and() to detect the src1p == src2p case? > __cpumask_clear_cpu(this_cpu, cfd->cpumask); > > cpumask_clear(cfd->cpumask_ipi); > -- > 2.34.1 >
On Mon, Jul 18, 2022 at 12:28:36PM -0700, Yury Norov wrote: > smp_call_function_many_cond() is often passed with cpu_online_mask. > If it's the case, we can use cpumask_copy instead of cpumask_and, which > is faster. > > Caught with CONFIG_DEBUG_BITMAP: > [ 7.830337] Call trace: > [ 7.830397] __bitmap_check_params+0x1d8/0x260 > [ 7.830499] smp_call_function_many_cond+0x1e8/0x45c > [ 7.830607] kick_all_cpus_sync+0x44/0x80 > [ 7.830698] bpf_int_jit_compile+0x34c/0x5cc > [ 7.830796] bpf_prog_select_runtime+0x118/0x190 > [ 7.830900] bpf_prepare_filter+0x3dc/0x51c > [ 7.830995] __get_filter+0xd4/0x170 > [ 7.831145] sk_attach_filter+0x18/0xb0 > [ 7.831236] sock_setsockopt+0x5b0/0x1214 > [ 7.831330] __sys_setsockopt+0x144/0x170 > [ 7.831431] __arm64_sys_setsockopt+0x2c/0x40 > [ 7.831541] invoke_syscall+0x48/0x114 > [ 7.831634] el0_svc_common.constprop.0+0x44/0xfc > [ 7.831745] do_el0_svc+0x30/0xc0 > [ 7.831825] el0_svc+0x2c/0x84 > [ 7.831899] el0t_64_sync_handler+0xbc/0x140 > [ 7.831999] el0t_64_sync+0x18c/0x190 > [ 7.832086] ---[ end trace 0000000000000000 ]--- > [ 7.832375] b1: ffff24d1ffd98a48 > [ 7.832385] b2: ffffa65533a29a38 > [ 7.832393] b3: ffffa65533a29a38 > [ 7.832400] nbits: 256 > [ 7.832407] start: 0 > [ 7.832412] off: 0 > [ 7.832418] smp: Bitmap: parameters check failed > [ 7.832432] smp: include/linux/bitmap.h [363]: bitmap_and Same for long commit message noise.
On Mon, Jul 18, 2022 at 11:29:06PM +0200, Peter Zijlstra wrote: > On Mon, Jul 18, 2022 at 12:28:36PM -0700, Yury Norov wrote: > > > --- > > kernel/smp.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/smp.c b/kernel/smp.c > > index 7ed2b9b12f74..f96fdf944b4a 100644 > > --- a/kernel/smp.c > > +++ b/kernel/smp.c > > @@ -942,7 +942,11 @@ static void smp_call_function_many_cond(const struct cpumask *mask, > > > > if (run_remote) { > > cfd = this_cpu_ptr(&cfd_data); > > - cpumask_and(cfd->cpumask, mask, cpu_online_mask); > > + if (mask == cpu_online_mask) > > + cpumask_copy(cfd->cpumask, cpu_online_mask); > > + else > > + cpumask_and(cfd->cpumask, mask, cpu_online_mask); > > + > > Or... you could optimize cpumask_and() to detect the src1p == src2p case? This is not what I would consider as optimization. For vast majority of users this check is useless because they know for sure that cpumasks are different. For this case I can invent something like cpumask_and_check_eq(), so that there'll be minimal impact on user code. (Suggestions for a better name are very welcome.) Thanks, Yury
diff --git a/kernel/smp.c b/kernel/smp.c index 7ed2b9b12f74..f96fdf944b4a 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -942,7 +942,11 @@ static void smp_call_function_many_cond(const struct cpumask *mask, if (run_remote) { cfd = this_cpu_ptr(&cfd_data); - cpumask_and(cfd->cpumask, mask, cpu_online_mask); + if (mask == cpu_online_mask) + cpumask_copy(cfd->cpumask, cpu_online_mask); + else + cpumask_and(cfd->cpumask, mask, cpu_online_mask); + __cpumask_clear_cpu(this_cpu, cfd->cpumask); cpumask_clear(cfd->cpumask_ipi);
smp_call_function_many_cond() is often passed with cpu_online_mask. If it's the case, we can use cpumask_copy instead of cpumask_and, which is faster. Caught with CONFIG_DEBUG_BITMAP: [ 7.830337] Call trace: [ 7.830397] __bitmap_check_params+0x1d8/0x260 [ 7.830499] smp_call_function_many_cond+0x1e8/0x45c [ 7.830607] kick_all_cpus_sync+0x44/0x80 [ 7.830698] bpf_int_jit_compile+0x34c/0x5cc [ 7.830796] bpf_prog_select_runtime+0x118/0x190 [ 7.830900] bpf_prepare_filter+0x3dc/0x51c [ 7.830995] __get_filter+0xd4/0x170 [ 7.831145] sk_attach_filter+0x18/0xb0 [ 7.831236] sock_setsockopt+0x5b0/0x1214 [ 7.831330] __sys_setsockopt+0x144/0x170 [ 7.831431] __arm64_sys_setsockopt+0x2c/0x40 [ 7.831541] invoke_syscall+0x48/0x114 [ 7.831634] el0_svc_common.constprop.0+0x44/0xfc [ 7.831745] do_el0_svc+0x30/0xc0 [ 7.831825] el0_svc+0x2c/0x84 [ 7.831899] el0t_64_sync_handler+0xbc/0x140 [ 7.831999] el0t_64_sync+0x18c/0x190 [ 7.832086] ---[ end trace 0000000000000000 ]--- [ 7.832375] b1: ffff24d1ffd98a48 [ 7.832385] b2: ffffa65533a29a38 [ 7.832393] b3: ffffa65533a29a38 [ 7.832400] nbits: 256 [ 7.832407] start: 0 [ 7.832412] off: 0 [ 7.832418] smp: Bitmap: parameters check failed [ 7.832432] smp: include/linux/bitmap.h [363]: bitmap_and Signed-off-by: Yury Norov <yury.norov@gmail.com> --- kernel/smp.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)