From 17bfe554b9a8c57c4d377bce930046138298fd8b Mon Sep 17 00:00:00 2001 From: Christian Biesinger Date: Tue, 15 Oct 2019 10:02:33 -0500 Subject: [PATCH] Allow not saving the signal state in SIGSETJMP Saving the signal state is very slow (this patch is a 14% speedup). The reason we need this code is because signal handler will leave the signal blocked when we longjmp out of it. But in this case we can just manually unblock the signal instead of taking the unconditional perf hit. gdb/ChangeLog: 2019-10-16 Christian Biesinger * gdbsupport/gdb_setjmp.h (SIGSETJMP): Allow passing in the value to pass on to sigsetjmp's second argument. * cp-support.c (gdb_demangle): Unblock SIGSEGV if we caught a crash. Change-Id: Ib3010966050c64b4cc8b47d8cb45871652b0b3ea --- gdb/ChangeLog | 6 ++++++ gdb/cp-support.c | 19 ++++++++++++++++++- gdb/gdbsupport/gdb_setjmp.h | 6 ++++-- 3 files changed, 28 insertions(+), 3 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index d11dbfbfcfd..ba028ed230f 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,9 @@ +2019-10-16 Christian Biesinger + + * gdbsupport/gdb_setjmp.h (SIGSETJMP): Allow passing in the value to + pass on to sigsetjmp's second argument. + * cp-support.c (gdb_demangle): Unblock SIGSEGV if we caught a crash. + 2019-10-16 Keith Seitz PR gdb/23567 diff --git a/gdb/cp-support.c b/gdb/cp-support.c index cd732b60e7d..253369b1efe 100644 --- a/gdb/cp-support.c +++ b/gdb/cp-support.c @@ -1539,7 +1539,16 @@ gdb_demangle (const char *name, int options) ofunc = signal (SIGSEGV, gdb_demangle_signal_handler); #endif - crash_signal = SIGSETJMP (gdb_demangle_jmp_buf); + /* The signal handler may keep the signal blocked when we longjmp out + of it. If we have sigprocmask, we can use it to unblock the signal + afterwards and we can avoid the performance overhead of saving the + signal mask just in case the signal gets triggered. Otherwise, just + tell sigsetjmp to save the mask. */ +#ifdef HAVE_SIGPROCMASK + crash_signal = SIGSETJMP (gdb_demangle_jmp_buf, 0); +#else + crash_signal = SIGSETJMP (gdb_demangle_jmp_buf, 1); +#endif } #endif @@ -1559,6 +1568,14 @@ gdb_demangle (const char *name, int options) { static int error_reported = 0; +#ifdef HAVE_SIGPROCMASK + /* If we got the signal, SIGSEGV may still be blocked; restore it. */ + sigset_t segv_sig_set; + sigemptyset (&segv_sig_set); + sigaddset (&segv_sig_set, SIGSEGV); + sigprocmask (SIG_UNBLOCK, &segv_sig_set, NULL); +#endif + if (!error_reported) { std::string short_msg diff --git a/gdb/gdbsupport/gdb_setjmp.h b/gdb/gdbsupport/gdb_setjmp.h index d4ebbfa8f2a..499597085b8 100644 --- a/gdb/gdbsupport/gdb_setjmp.h +++ b/gdb/gdbsupport/gdb_setjmp.h @@ -23,11 +23,13 @@ #ifdef HAVE_SIGSETJMP #define SIGJMP_BUF sigjmp_buf -#define SIGSETJMP(buf) sigsetjmp((buf), 1) +#define SIGSETJMP(buf,val) sigsetjmp((buf), val) #define SIGLONGJMP(buf,val) siglongjmp((buf), (val)) #else #define SIGJMP_BUF jmp_buf -#define SIGSETJMP(buf) setjmp(buf) +/* We ignore val here because that's safer and avoids having to check + whether _setjmp exists. */ +#define SIGSETJMP(buf,val) setjmp(buf) #define SIGLONGJMP(buf,val) longjmp((buf), (val)) #endif -- 2.30.2