[PATCH 1/2] allow honouring libc provided SIGRTMIN/SIGRTMAX
Rasmus Villemoes
rasmus.villemoes at prevas.dk
Wed Sep 12 14:06:36 UTC 2018
When an application documents that it responds such and such to
SIGRTMIN+n, that almost always means with respect to the libc-provided
SIGRTMIN. Hence I disagree with the "more correct" in commit
7b276fc17594. In any case, this is rather unfortunate:
# kill -l RTMIN+2
36
# busybox kill -l RTMIN+2
34
(the first shell is bash). We probably can't change default behaviour
after 7 years, but at least we can provide a config option.
We avoid a little code generation (repeated calls to
__libc_current_sigrtmin) by stashing SIGRTMIN/SIGRTMAX in local
variables, but it does cost ~50 bytes. The next patch serves as penance
for that.
Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
---
libbb/u_signal_names.c | 49 ++++++++++++++++++++++++++++++++++++-------------
1 file changed, 36 insertions(+), 13 deletions(-)
diff --git a/libbb/u_signal_names.c b/libbb/u_signal_names.c
index b3038e32d..5ef5c3f28 100644
--- a/libbb/u_signal_names.c
+++ b/libbb/u_signal_names.c
@@ -12,6 +12,15 @@
//config: help
//config: Support RTMIN[+n] and RTMAX[-n] signal names
//config: in kill, killall etc. This costs ~250 bytes.
+//config:config FEATURE_RTMINMAX_USE_LIBC_DEFINITIONS
+//config: bool "Use the definitions of SIGRTMIN/SIGRTMAX provided by libc"
+//config: depends on FEATURE_RTMINMAX
+//config: help
+//config: Some C libraries reserve a few real-time signals for internal
+//config: use, and adjust the values of SIGRTMIN/SIGRTMAX seen by
+//config: applications accordingly. Saying yes here means that a signal
+//config: name RTMIN+n will be interpreted according to the libc definition
+//config: of SIGRTMIN, and not the raw definition provided by the kernel.
#include "libbb.h"
@@ -123,7 +132,7 @@ static const char signals[][7] ALIGN1 = {
#ifdef SIGSYS
[SIGSYS ] = "SYS",
#endif
-#if ENABLE_FEATURE_RTMINMAX
+#if ENABLE_FEATURE_RTMINMAX && !ENABLE_FEATURE_RTMINMAX_USE_LIBC_DEFINITIONS
# ifdef __SIGRTMIN
[__SIGRTMIN] = "RTMIN",
# endif
@@ -140,6 +149,7 @@ static const char signals[][7] ALIGN1 = {
int FAST_FUNC get_signum(const char *name)
{
unsigned i;
+ unsigned sigrtmin, sigrtmax;
i = bb_strtou(name, NULL, 10);
if (!errno && i < NSIG) /* for shells, we allow 0 too */
@@ -168,10 +178,13 @@ int FAST_FUNC get_signum(const char *name)
# endif
#endif
-#if ENABLE_FEATURE_RTMINMAX
-# if defined(SIGRTMIN) && defined(SIGRTMAX)
-/* libc may use some rt sigs for pthreads and therefore "remap" SIGRTMIN/MAX,
- * but we want to use "raw" SIGRTMIN/MAX. Underscored names, if exist, provide
+#if ENABLE_FEATURE_RTMINMAX && defined(SIGRTMIN) && defined(SIGRTMAX)
+# if ENABLE_FEATURE_RTMINMAX_USE_LIBC_DEFINITIONS
+/* Use the libc provided values. */
+ sigrtmin = SIGRTMIN;
+ sigrtmax = SIGRTMAX;
+# else
+/* Use the "raw SIGRTMIN/MAX. Underscored names, if exist, provide
* them. If they don't exist, fall back to non-underscored ones: */
# if !defined(__SIGRTMIN)
# define __SIGRTMIN SIGRTMIN
@@ -179,25 +192,27 @@ int FAST_FUNC get_signum(const char *name)
# if !defined(__SIGRTMAX)
# define __SIGRTMAX SIGRTMAX
# endif
+ sigrtmin = __SIGRTMIN;
+ sigrtmax = __SIGRTMAX;
+# endif
if (strncasecmp(name, "RTMIN", 5) == 0) {
if (!name[5])
- return __SIGRTMIN;
+ return sigrtmin;
if (name[5] == '+') {
i = bb_strtou(name + 6, NULL, 10);
- if (!errno && i <= __SIGRTMAX - __SIGRTMIN)
- return __SIGRTMIN + i;
+ if (!errno && i <= sigrtmax - sigrtmin)
+ return sigrtmin + i;
}
}
else if (strncasecmp(name, "RTMAX", 5) == 0) {
if (!name[5])
- return __SIGRTMAX;
+ return sigrtmax;
if (name[5] == '-') {
i = bb_strtou(name + 6, NULL, 10);
- if (!errno && i <= __SIGRTMAX - __SIGRTMIN)
- return __SIGRTMAX - i;
+ if (!errno && i <= sigrtmax - sigrtmin)
+ return sigrtmax - i;
}
}
-# endif
#endif
return -1;
@@ -228,8 +243,16 @@ void FAST_FUNC print_signames(void)
printf("%2u) %s\n", signo, name);
}
#if ENABLE_FEATURE_RTMINMAX
-# ifdef __SIGRTMAX
+# if ENABLE_FEATURE_RTMINMAX_USE_LIBC_DEFINITIONS
+# if defined(SIGRTMIN) && defined(SIGRTMAX)
+ printf("%2u) %s\n", SIGRTMIN, "RTMIN");
+ printf("%2u) %s\n", SIGRTMAX, "RTMAX");
+# endif
+# else
+// __SIGRTMIN is included in signals[] array.
+# ifdef __SIGRTMAX
printf("%2u) %s\n", __SIGRTMAX, "RTMAX");
+# endif
# endif
#endif
}
--
2.16.4
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