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Merge pull request #18060 from opensourcerouting/lib-crashlog-signals

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lib: crash handlers must be allowed on threads
This commit is contained in:
Donald Sharp 2025-02-11 12:25:28 -05:00 committed by GitHub
parent c2159b7f53 13a6ac5b4c
commit f64104bd97
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GPG key ID: B5690EEEBB952194
3 changed files with 45 additions and 5 deletions
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8
lib/frr_pthread.c
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@ -20,6 +20,7 @@
#include "zlog.h"
#include "libfrr.h"
#include "libfrr_trace.h"
#include "sigevent.h"
DEFINE_MTYPE_STATIC(LIB, FRR_PTHREAD, "FRR POSIX Thread");
DEFINE_MTYPE_STATIC(LIB, PTHREAD_PRIM, "POSIX sync primitives");
@ -185,10 +186,9 @@ int frr_pthread_run(struct frr_pthread *fpt, const pthread_attr_t *attr)
assert(frr_is_after_fork || !"trying to start thread before fork()");
/* Ensure we never handle signals on a background thread by blocking
* everything here (new thread inherits signal mask)
*/
sigfillset(&blocksigs);
sigemptyset(&blocksigs);
frr_sigset_add_mainonly(&blocksigs);
/* new thread inherits mask */
pthread_sigmask(SIG_BLOCK, &blocksigs, &oldsigs);
frrtrace(1, frr_libfrr, frr_pthread_run, fpt->name);

15
lib/frrcu.c
View file

@ -42,6 +42,7 @@
#include "frrcu.h"
#include "seqlock.h"
#include "atomlist.h"
#include "sigevent.h"
DEFINE_MTYPE_STATIC(LIB, RCU_THREAD, "RCU thread");
DEFINE_MTYPE_STATIC(LIB, RCU_NEXT, "RCU sequence barrier");
@ -346,7 +347,19 @@ static void rcu_start(void)
*/
sigset_t oldsigs, blocksigs;
sigfillset(&blocksigs);
/* technically, the RCU thread is very poorly suited to run even just a
* crashlog handler, since zlog_sigsafe() could deadlock on transiently
* invalid (due to RCU) logging data structures
*
* but given that when we try to write a crashlog, we're already in
* b0rked territory anyway - give the crashlog handler a chance.
*
* (also cf. the SIGALRM usage in writing crashlogs to avoid hung
* processes on any kind of deadlock in crash handlers)
*/
sigemptyset(&blocksigs);
frr_sigset_add_mainonly(&blocksigs);
/* new thread inherits mask */
pthread_sigmask(SIG_BLOCK, &blocksigs, &oldsigs);
rcu_active = true;

27
lib/sigevent.h
View file

@ -45,6 +45,33 @@ bool frr_sigevent_check(sigset_t *setp);
/* check whether there are signals to handle, process any found */
extern int frr_sigevent_process(void);
/* Ensure we don't handle "application-type" signals on a secondary thread by
* blocking these signals when creating threads
*
* NB: SIGSEGV, SIGABRT, etc. must be allowed on all threads or we get no
* crashlogs. Since signals vary a little bit between platforms, below is a
* list of known things to go to the main thread. Any unknown signals should
* stay thread-local.
*/
static inline void frr_sigset_add_mainonly(sigset_t *blocksigs)
{
/* signals we actively handle */
sigaddset(blocksigs, SIGHUP);
sigaddset(blocksigs, SIGINT);
sigaddset(blocksigs, SIGTERM);
sigaddset(blocksigs, SIGUSR1);
/* signals we don't actively use but that semantically belong */
sigaddset(blocksigs, SIGUSR2);
sigaddset(blocksigs, SIGQUIT);
sigaddset(blocksigs, SIGCHLD);
sigaddset(blocksigs, SIGPIPE);
sigaddset(blocksigs, SIGTSTP);
sigaddset(blocksigs, SIGTTIN);
sigaddset(blocksigs, SIGTTOU);
sigaddset(blocksigs, SIGWINCH);
}
#ifdef __cplusplus
}
#endif