From ad12d7d4b020e6be225a8d6494de69d051ec7f81 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Wed, 22 Apr 2009 19:10:09 +0200 Subject: memtrap,aupdate: split atomic update from memtrap into seperate aupdate framework --- src/pulsecore/memtrap.c | 116 +++++++++++++++--------------------------------- 1 file changed, 35 insertions(+), 81 deletions(-) (limited to 'src/pulsecore/memtrap.c') diff --git a/src/pulsecore/memtrap.c b/src/pulsecore/memtrap.c index e04e838e..bd0243e0 100644 --- a/src/pulsecore/memtrap.c +++ b/src/pulsecore/memtrap.c @@ -28,10 +28,10 @@ #include -#include -#include -#include #include +#include +#include +#include #include "memtrap.h" @@ -43,13 +43,13 @@ struct pa_memtrap { }; static pa_memtrap *memtraps[2] = { NULL, NULL }; -static pa_atomic_t read_lock = PA_ATOMIC_INIT(0); -static pa_static_semaphore semaphore = PA_STATIC_SEMAPHORE_INIT; -static pa_static_mutex write_lock = PA_STATIC_MUTEX_INIT; +static pa_aupdate *aupdate; -#define MSB (1U << (sizeof(unsigned)*8U-1)) -#define WHICH(n) (!!((n) & MSB)) -#define COUNTER(n) ((n) & ~MSB) +static void allocate_aupdate(void) { + PA_ONCE_BEGIN { + aupdate = pa_aupdate_new(); + } PA_ONCE_END; +} pa_bool_t pa_memtrap_is_good(pa_memtrap *m) { pa_assert(m); @@ -62,19 +62,11 @@ static void sigsafe_error(const char *s) { } static void signal_handler(int sig, siginfo_t* si, void *data) { - unsigned n, j; + unsigned j; pa_memtrap *m; void *r; - /* Increase the lock counter */ - n = (unsigned) pa_atomic_inc(&read_lock); - - /* The uppermost bit tells us which list to look at */ - j = WHICH(n); - - /* When n is 0 we have about 2^31 threads running that - * all got a sigbus at the same time, oh my! */ - pa_assert(COUNTER(n)+1 > 0); + j = pa_aupdate_read_begin(aupdate); for (m = memtraps[j]; m; m = m->next[j]) if (si->si_addr >= m->start && @@ -94,33 +86,16 @@ static void signal_handler(int sig, siginfo_t* si, void *data) { pa_assert(r == m->start); - pa_atomic_dec(&read_lock); - - /* Post the semaphore */ - pa_semaphore_post(pa_static_semaphore_get(&semaphore, 0)); - + pa_aupdate_read_end(aupdate); return; fail: + pa_aupdate_read_end(aupdate); + sigsafe_error("Failed to handle SIGBUS.\n"); - pa_atomic_dec(&read_lock); abort(); } -static void memtrap_swap(unsigned n) { - - for (;;) { - - /* If the read counter is > 0 wait; if it is 0 try to swap the lists */ - if (COUNTER(n) > 0) - pa_semaphore_wait(pa_static_semaphore_get(&semaphore, 0)); - else if (pa_atomic_cmpxchg(&read_lock, (int) n, (int) (n ^ MSB))) - break; - - n = (unsigned) pa_atomic_load(&read_lock); - } -} - static void memtrap_link(pa_memtrap *m, unsigned j) { pa_assert(m); @@ -143,58 +118,47 @@ static void memtrap_unlink(pa_memtrap *m, unsigned j) { pa_memtrap* pa_memtrap_add(const void *start, size_t size) { pa_memtrap *m = NULL; - pa_mutex *lock; - unsigned n, j; + unsigned j; pa_assert(start); pa_assert(size > 0); pa_assert(PA_PAGE_ALIGN_PTR(start) == start); pa_assert(PA_PAGE_ALIGN(size) == size); - lock = pa_static_mutex_get(&write_lock, FALSE, FALSE); - pa_mutex_lock(lock); - - n = (unsigned) pa_atomic_load(&read_lock); - j = WHICH(n); - m = pa_xnew(pa_memtrap, 1); m->start = (void*) start; m->size = size; pa_atomic_store(&m->bad, 0); - memtrap_link(m, !j); - memtrap_swap(n); - memtrap_link(m, j); + allocate_aupdate(); - pa_mutex_unlock(lock); + j = pa_aupdate_write_begin(aupdate); + memtrap_link(m, j); + j = pa_aupdate_write_swap(aupdate); + memtrap_link(m, j); + pa_aupdate_write_end(aupdate); return m; } void pa_memtrap_remove(pa_memtrap *m) { - unsigned n, j; - pa_mutex *lock; + unsigned j; pa_assert(m); - lock = pa_static_mutex_get(&write_lock, FALSE, FALSE); - pa_mutex_lock(lock); + allocate_aupdate(); - n = (unsigned) pa_atomic_load(&read_lock); - j = WHICH(n); - - memtrap_unlink(m, !j); - memtrap_swap(n); + j = pa_aupdate_write_begin(aupdate); + memtrap_unlink(m, j); + j = pa_aupdate_write_swap(aupdate); memtrap_unlink(m, j); + pa_aupdate_write_end(aupdate); pa_xfree(m); - - pa_mutex_unlock(lock); } pa_memtrap *pa_memtrap_update(pa_memtrap *m, const void *start, size_t size) { - unsigned n, j; - pa_mutex *lock; + unsigned j; pa_assert(m); @@ -203,32 +167,25 @@ pa_memtrap *pa_memtrap_update(pa_memtrap *m, const void *start, size_t size) { pa_assert(PA_PAGE_ALIGN_PTR(start) == start); pa_assert(PA_PAGE_ALIGN(size) == size); - lock = pa_static_mutex_get(&write_lock, FALSE, FALSE); - pa_mutex_lock(lock); + allocate_aupdate(); + + j = pa_aupdate_write_begin(aupdate); if (m->start == start && m->size == size) goto unlock; - n = (unsigned) pa_atomic_load(&read_lock); - j = WHICH(n); - - memtrap_unlink(m, !j); - memtrap_swap(n); memtrap_unlink(m, j); + j = pa_aupdate_write_swap(aupdate); m->start = (void*) start; m->size = size; pa_atomic_store(&m->bad, 0); - n = (unsigned) pa_atomic_load(&read_lock); - j = WHICH(n); - - memtrap_link(m, !j); - memtrap_swap(n); + j = pa_aupdate_write_swap(aupdate); memtrap_link(m, j); unlock: - pa_mutex_unlock(lock); + pa_aupdate_write_end(aupdate); return m; } @@ -236,10 +193,7 @@ unlock: void pa_memtrap_install(void) { struct sigaction sa; - /* Before we install the signal handler, make sure the semaphore - * is valid so that the initialization of the semaphore - * doesn't have to happen from the signal handler */ - pa_static_semaphore_get(&semaphore, 0); + allocate_aupdate(); memset(&sa, 0, sizeof(sa)); sa.sa_sigaction = signal_handler; -- cgit