| Message ID | 20230720163056.2564824-7-vschneid@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | context_tracking,x86: Defer some IPIs until a user->kernel transition | expand |
On Thu, 20 Jul 2023 17:30:42 +0100 Valentin Schneider <vschneid@redhat.com> wrote: > Steven noted that when the user-provided cpumask contains a single CPU, > then the filtering function can use a scalar as input instead of a > full-fledged cpumask. > > When the mask contains a single CPU, directly re-use the unsigned field > predicate functions. Transform '&' into '==' beforehand. > > Suggested-by: Steven Rostedt <rostedt@goodmis.org> > Signed-off-by: Valentin Schneider <vschneid@redhat.com> > --- > kernel/trace/trace_events_filter.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c > index 2fe65ddeb34ef..54d642fabb7f1 100644 > --- a/kernel/trace/trace_events_filter.c > +++ b/kernel/trace/trace_events_filter.c > @@ -1750,7 +1750,7 @@ static int parse_pred(const char *str, void *data, > * then we can treat it as a scalar input. > */ > single = cpumask_weight(pred->mask) == 1; > - if (single && field->filter_type == FILTER_CPUMASK) { > + if (single && field->filter_type != FILTER_CPU) { > pred->val = cpumask_first(pred->mask); > kfree(pred->mask); > } > @@ -1761,6 +1761,11 @@ static int parse_pred(const char *str, void *data, > FILTER_PRED_FN_CPUMASK; > } else if (field->filter_type == FILTER_CPU) { > pred->fn_num = FILTER_PRED_FN_CPU_CPUMASK; > + } else if (single) { > + pred->op = pred->op == OP_BAND ? OP_EQ : pred->op; Nit, the above can be written as: pred->op = pret->op != OP_BAND ? : OP_EQ; -- Steve > + pred->fn_num = select_comparison_fn(pred->op, field->size, false); > + if (pred->op == OP_NE) > + pred->not = 1; > } else { > switch (field->size) { > case 8:
On 29/07/23 15:55, Steven Rostedt wrote: > On Thu, 20 Jul 2023 17:30:42 +0100 > Valentin Schneider <vschneid@redhat.com> wrote: > >> Steven noted that when the user-provided cpumask contains a single CPU, >> then the filtering function can use a scalar as input instead of a >> full-fledged cpumask. >> >> When the mask contains a single CPU, directly re-use the unsigned field >> predicate functions. Transform '&' into '==' beforehand. >> >> Suggested-by: Steven Rostedt <rostedt@goodmis.org> >> Signed-off-by: Valentin Schneider <vschneid@redhat.com> >> --- >> kernel/trace/trace_events_filter.c | 7 ++++++- >> 1 file changed, 6 insertions(+), 1 deletion(-) >> >> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c >> index 2fe65ddeb34ef..54d642fabb7f1 100644 >> --- a/kernel/trace/trace_events_filter.c >> +++ b/kernel/trace/trace_events_filter.c >> @@ -1750,7 +1750,7 @@ static int parse_pred(const char *str, void *data, >> * then we can treat it as a scalar input. >> */ >> single = cpumask_weight(pred->mask) == 1; >> - if (single && field->filter_type == FILTER_CPUMASK) { >> + if (single && field->filter_type != FILTER_CPU) { >> pred->val = cpumask_first(pred->mask); >> kfree(pred->mask); >> } >> @@ -1761,6 +1761,11 @@ static int parse_pred(const char *str, void *data, >> FILTER_PRED_FN_CPUMASK; >> } else if (field->filter_type == FILTER_CPU) { >> pred->fn_num = FILTER_PRED_FN_CPU_CPUMASK; >> + } else if (single) { >> + pred->op = pred->op == OP_BAND ? OP_EQ : pred->op; > > Nit, the above can be written as: > > pred->op = pret->op != OP_BAND ? : OP_EQ; > That's neater, thanks! > -- Steve > > >> + pred->fn_num = select_comparison_fn(pred->op, field->size, false); >> + if (pred->op == OP_NE) >> + pred->not = 1; >> } else { >> switch (field->size) { >> case 8:
On Sat, Jul 29, 2023 at 03:55:47PM -0400, Steven Rostedt wrote: > > @@ -1761,6 +1761,11 @@ static int parse_pred(const char *str, void *data, > > FILTER_PRED_FN_CPUMASK; > > } else if (field->filter_type == FILTER_CPU) { > > pred->fn_num = FILTER_PRED_FN_CPU_CPUMASK; > > + } else if (single) { > > + pred->op = pred->op == OP_BAND ? OP_EQ : pred->op; > > Nit, the above can be written as: > > pred->op = pret->op != OP_BAND ? : OP_EQ; > Heh. Those are not equivalent. The right way to write this is: if (pred->op == OP_BAND) pred->op = OP_EQ; regards, dan carpenter
On Mon, 31 Jul 2023 15:07:52 +0300 Dan Carpenter <dan.carpenter@linaro.org> wrote: > On Sat, Jul 29, 2023 at 03:55:47PM -0400, Steven Rostedt wrote: > > > @@ -1761,6 +1761,11 @@ static int parse_pred(const char *str, void *data, > > > FILTER_PRED_FN_CPUMASK; > > > } else if (field->filter_type == FILTER_CPU) { > > > pred->fn_num = FILTER_PRED_FN_CPU_CPUMASK; > > > + } else if (single) { > > > + pred->op = pred->op == OP_BAND ? OP_EQ : pred->op; > > > > Nit, the above can be written as: > > > > pred->op = pret->op != OP_BAND ? : OP_EQ; > > > > Heh. Those are not equivalent. The right way to write this is: You mean because of my typo? > > if (pred->op == OP_BAND) > pred->op = OP_EQ; But sure, I'm fine with that, and it's probably more readable too. -- Steve
On Mon, Jul 31, 2023 at 11:54:53AM -0400, Steven Rostedt wrote: > On Mon, 31 Jul 2023 15:07:52 +0300 > Dan Carpenter <dan.carpenter@linaro.org> wrote: > > > On Sat, Jul 29, 2023 at 03:55:47PM -0400, Steven Rostedt wrote: > > > > @@ -1761,6 +1761,11 @@ static int parse_pred(const char *str, void *data, > > > > FILTER_PRED_FN_CPUMASK; > > > > } else if (field->filter_type == FILTER_CPU) { > > > > pred->fn_num = FILTER_PRED_FN_CPU_CPUMASK; > > > > + } else if (single) { > > > > + pred->op = pred->op == OP_BAND ? OP_EQ : pred->op; > > > > > > Nit, the above can be written as: > > > > > > pred->op = pret->op != OP_BAND ? : OP_EQ; > > > > > > > Heh. Those are not equivalent. The right way to write this is: > > You mean because of my typo? No, I hadn't seen the s/pred/pret/ typo. Your code does: if (pred->op != OP_BAND) pred->op = true; else pred->op OP_EQ; Realy we should probably trigger a static checker warning any time someone does a compare operations as part of a "x = comparison ?: bar; Years ago, someone asked me to do that with regards to error codes like: return ret < 0 ?: -EINVAL; but I don't remember the results. regards, dan carpenter
On 31/07/23 19:03, Dan Carpenter wrote: > On Mon, Jul 31, 2023 at 11:54:53AM -0400, Steven Rostedt wrote: >> On Mon, 31 Jul 2023 15:07:52 +0300 >> Dan Carpenter <dan.carpenter@linaro.org> wrote: >> >> > On Sat, Jul 29, 2023 at 03:55:47PM -0400, Steven Rostedt wrote: >> > > > @@ -1761,6 +1761,11 @@ static int parse_pred(const char *str, void *data, >> > > > FILTER_PRED_FN_CPUMASK; >> > > > } else if (field->filter_type == FILTER_CPU) { >> > > > pred->fn_num = FILTER_PRED_FN_CPU_CPUMASK; >> > > > + } else if (single) { >> > > > + pred->op = pred->op == OP_BAND ? OP_EQ : pred->op; >> > > >> > > Nit, the above can be written as: >> > > >> > > pred->op = pret->op != OP_BAND ? : OP_EQ; >> > > >> > >> > Heh. Those are not equivalent. The right way to write this is: >> >> You mean because of my typo? > > No, I hadn't seen the s/pred/pret/ typo. Your code does: > > if (pred->op != OP_BAND) > pred->op = true; > else > pred->op OP_EQ; > > Realy we should probably trigger a static checker warning any time > someone does a compare operations as part of a "x = comparison ?: bar; > Years ago, someone asked me to do that with regards to error codes like: > > return ret < 0 ?: -EINVAL; > > but I don't remember the results. > FWIW this is caught by GCC: error: the omitted middle operand in ?: will always be ‘true’, suggest explicit middle operand [-Werror=parentheses] pred->op = pred->op != OP_BAND ? : OP_EQ; > regards, > dan carpenter
On Mon, 31 Jul 2023 19:03:04 +0300 Dan Carpenter <dan.carpenter@linaro.org> wrote: > > > > Nit, the above can be written as: > > > > > > > > pred->op = pret->op != OP_BAND ? : OP_EQ; > > > > > > > > > > Heh. Those are not equivalent. The right way to write this is: > > > > You mean because of my typo? > > No, I hadn't seen the s/pred/pret/ typo. Your code does: > > if (pred->op != OP_BAND) > pred->op = true; > else > pred->op OP_EQ; Ah, for some reason I was thinking the ? : just was just a nop, but I guess it is to assign the cond value :-/ But of course every place I've done that, it was the condition value I wanted, which was the same as the value being assigned. Thanks, -- Steve
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index 2fe65ddeb34ef..54d642fabb7f1 100644 --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c @@ -1750,7 +1750,7 @@ static int parse_pred(const char *str, void *data, * then we can treat it as a scalar input. */ single = cpumask_weight(pred->mask) == 1; - if (single && field->filter_type == FILTER_CPUMASK) { + if (single && field->filter_type != FILTER_CPU) { pred->val = cpumask_first(pred->mask); kfree(pred->mask); } @@ -1761,6 +1761,11 @@ static int parse_pred(const char *str, void *data, FILTER_PRED_FN_CPUMASK; } else if (field->filter_type == FILTER_CPU) { pred->fn_num = FILTER_PRED_FN_CPU_CPUMASK; + } else if (single) { + pred->op = pred->op == OP_BAND ? OP_EQ : pred->op; + pred->fn_num = select_comparison_fn(pred->op, field->size, false); + if (pred->op == OP_NE) + pred->not = 1; } else { switch (field->size) { case 8:
Steven noted that when the user-provided cpumask contains a single CPU, then the filtering function can use a scalar as input instead of a full-fledged cpumask. When the mask contains a single CPU, directly re-use the unsigned field predicate functions. Transform '&' into '==' beforehand. Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Valentin Schneider <vschneid@redhat.com> --- kernel/trace/trace_events_filter.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)