Each time watchpoints are added/removed from the array it's done using an read-copy-update cycle. Simultaneous writes are protected by the debug_update_lock.
Signed-off-by: Alex Bennée <alex.ben...@linaro.org> --- cpu-exec.c | 7 ++- exec.c | 193 ++++++++++++++++++++++++++++++++++++++++++++----------------- 2 files changed, 144 insertions(+), 56 deletions(-) diff --git a/cpu-exec.c b/cpu-exec.c index 2736a27..7fcb500 100644 --- a/cpu-exec.c +++ b/cpu-exec.c @@ -387,12 +387,13 @@ static inline bool cpu_handle_halt(CPUState *cpu) static inline void cpu_handle_debug_exception(CPUState *cpu) { CPUClass *cc = CPU_GET_CLASS(cpu); + GArray *wpts = atomic_rcu_read(&cpu->watchpoints); CPUWatchpoint *wp; int i; - if (!cpu->watchpoint_hit && cpu->watchpoints) { - for (i = 0; i < cpu->watchpoints->len; i++) { - wp = &g_array_index(cpu->watchpoints, CPUWatchpoint, i); + if (!cpu->watchpoint_hit && wpts) { + for (i = 0; i < wpts->len; i++) { + wp = &g_array_index(wpts, CPUWatchpoint, i); wp->flags &= ~BP_WATCHPOINT_HIT; } } diff --git a/exec.c b/exec.c index d1d14c1..b9167ec 100644 --- a/exec.c +++ b/exec.c @@ -735,6 +735,18 @@ static void breakpoint_invalidate(CPUState *cpu, target_ulong pc) } #endif +struct FreeDebugRCU { + struct rcu_head rcu; + GArray *debug; +}; + +/* RCU reclaim step */ +static void rcu_debug_free(struct FreeDebugRCU *rcu_free) +{ + g_array_free(rcu_free->debug, false); + g_free(rcu_free); +} + #if defined(CONFIG_USER_ONLY) void cpu_watchpoint_remove_all(CPUState *cpu, int mask) @@ -766,22 +778,72 @@ CPUWatchpoint *cpu_watchpoint_get_by_ref(CPUState *cpu, int ref) return NULL; } #else -/* Find watchpoint with external reference */ -CPUWatchpoint *cpu_watchpoint_get_by_ref(CPUState *cpu, int ref) +/* Create a working copy of the watchpoints. + * + * The rcu_read_lock() may already be held depending on where this + * update has been triggered from. However it is safe to nest + * rcu_read_locks() so we do the copy under the lock here. + */ + +static GArray *rcu_copy_watchpoints(CPUState *cpu) { - CPUWatchpoint *wp = NULL; + GArray *old, *new; + + rcu_read_lock(); + old = atomic_rcu_read(&cpu->watchpoints); + if (old) { + new = g_array_sized_new(false, false, sizeof(CPUWatchpoint), old->len); + memcpy(new->data, old->data, old->len * sizeof(CPUWatchpoint)); + new->len = old->len; + } else { + new = g_array_new(false, false, sizeof(CPUWatchpoint)); + } + rcu_read_unlock(); + + return new; +} + +/* Called with update lock held */ +static void rcu_update_watchpoints(CPUState *cpu, GArray *new_watchpts) +{ + GArray *wpts = atomic_rcu_read(&cpu->watchpoints); + atomic_rcu_set(&cpu->watchpoints, new_watchpts); + if (wpts) { + struct FreeDebugRCU *rcu_free = g_malloc(sizeof(*rcu_free)); + rcu_free->debug = wpts; + call_rcu(rcu_free, rcu_debug_free, rcu); + } +} + +/* Find watchpoint with external reference, only valid for duration of + * rcu_read_lock */ +static CPUWatchpoint *find_watch_with_ref(GArray *wpts, int ref) +{ + CPUWatchpoint *wp; int i = 0; + do { - wp = &g_array_index(cpu->watchpoints, CPUWatchpoint, i++); - } while (i < cpu->watchpoints->len && wp && wp->ref != ref); + wp = &g_array_index(wpts, CPUWatchpoint, i); + if (wp->ref == ref) { + return wp; + } + } while (i++ < wpts->len); + + return NULL; +} - return wp; +/* Find watchpoint with external reference */ +CPUWatchpoint *cpu_watchpoint_get_by_ref(CPUState *cpu, int ref) +{ + GArray *wpts = atomic_rcu_read(&cpu->watchpoints); + return find_watch_with_ref(wpts, ref); } /* Add a watchpoint. */ int cpu_watchpoint_insert_with_ref(CPUState *cpu, vaddr addr, vaddr len, int flags, int ref) { + GArray *wpts; CPUWatchpoint *wp = NULL; /* forbid ranges which are empty or run off the end of the address space */ @@ -791,14 +853,14 @@ int cpu_watchpoint_insert_with_ref(CPUState *cpu, vaddr addr, vaddr len, return -EINVAL; } - /* Allocate if no previous watchpoints */ - if (!cpu->watchpoints) { - cpu->watchpoints = g_array_new(false, true, sizeof(CPUWatchpoint)); - } + qemu_mutex_lock(&cpu->update_debug_lock); + + /* This will allocate if no previous breakpoints */ + wpts = rcu_copy_watchpoints(cpu); /* Find old watchpoint */ if (ref != BPWP_NOREF) { - wp = cpu_watchpoint_get_by_ref(cpu, ref); + wp = find_watch_with_ref(wpts, ref); } if (wp) { @@ -815,15 +877,18 @@ int cpu_watchpoint_insert_with_ref(CPUState *cpu, vaddr addr, vaddr len, /* keep all GDB-injected watchpoints in front */ if (flags & BP_GDB) { - g_array_prepend_val(cpu->watchpoints, watch); + g_array_prepend_val(wpts, watch); } else { - g_array_append_val(cpu->watchpoints, watch); + g_array_append_val(wpts, watch); } } tlb_flush_page(cpu, addr); + rcu_update_watchpoints(cpu, wpts); + qemu_mutex_unlock(&cpu->update_debug_lock); + return 0; } @@ -832,69 +897,101 @@ int cpu_watchpoint_insert(CPUState *cpu, vaddr addr, vaddr len, int flags) return cpu_watchpoint_insert_with_ref(cpu, addr, len, flags, BPWP_NOREF); } -static void cpu_watchpoint_delete(CPUState *cpu, int index) +static void cpu_watchpoint_delete(CPUState *cpu, GArray *wpts, int index) { CPUWatchpoint *wp; - wp = &g_array_index(cpu->watchpoints, CPUWatchpoint, index); + wp = &g_array_index(wpts, CPUWatchpoint, index); tlb_flush_page(cpu, wp->vaddr); - g_array_remove_index(cpu->watchpoints, index); + g_array_remove_index(wpts, index); } /* Remove a specific watchpoint. */ int cpu_watchpoint_remove(CPUState *cpu, vaddr addr, vaddr len, int flags) { + GArray *wpts = atomic_rcu_read(&cpu->watchpoints); CPUWatchpoint *wp; - int i = 0; + int retval = -ENOENT; + + if (unlikely(wpts) && unlikely(wpts->len)) { + int i = 0; + + qemu_mutex_lock(&cpu->update_debug_lock); + wpts = rcu_copy_watchpoints(cpu); - if (unlikely(cpu->watchpoints) && unlikely(cpu->watchpoints->len)) { do { wp = &g_array_index(cpu->watchpoints, CPUWatchpoint, i); if (wp && addr == wp->vaddr && len == wp->len && flags == (wp->flags & ~BP_WATCHPOINT_HIT)) { - cpu_watchpoint_delete(cpu, i); - return 0; + cpu_watchpoint_delete(cpu, wpts, i); + retval = 0; + } else { + i++; } - } while (i++ < cpu->watchpoints->len); + } while (i < wpts->len); + + rcu_update_watchpoints(cpu, wpts); + qemu_mutex_unlock(&cpu->update_debug_lock); + } - return -ENOENT; + return retval; } /* Remove a specific watchpoint by external reference. */ int cpu_watchpoint_remove_by_ref(CPUState *cpu, int ref) { + GArray *wpts = atomic_rcu_read(&cpu->watchpoints); CPUWatchpoint *wp; - int i = 0; + int retval = -ENOENT; + + if (unlikely(wpts) && unlikely(wpts->len)) { + int i = 0; + + qemu_mutex_lock(&cpu->update_debug_lock); + wpts = rcu_copy_watchpoints(cpu); - if (unlikely(cpu->watchpoints) && unlikely(cpu->watchpoints->len)) { do { - wp = &g_array_index(cpu->watchpoints, CPUWatchpoint, i); + wp = &g_array_index(wpts, CPUWatchpoint, i); if (wp && wp->ref == ref) { - cpu_watchpoint_delete(cpu, i); - return 0; + cpu_watchpoint_delete(cpu, wpts, i); + retval = 0; + } else { + i++; } - } while (wp && i++ < cpu->watchpoints->len); + } while (i < wpts->len); + + rcu_update_watchpoints(cpu, wpts); + qemu_mutex_unlock(&cpu->update_debug_lock); + } - return -ENOENT; + return retval; } /* Remove all matching watchpoints. */ void cpu_watchpoint_remove_all(CPUState *cpu, int mask) { + GArray *wpts = atomic_rcu_read(&cpu->watchpoints); CPUWatchpoint *wp; - if (unlikely(cpu->watchpoints) && unlikely(cpu->watchpoints->len)) { - int i = cpu->watchpoints->len; + if (unlikely(wpts) && unlikely(wpts->len)) { + int i = 0; + + qemu_mutex_lock(&cpu->update_debug_lock); + wpts = rcu_copy_watchpoints(cpu); + do { - wp = &g_array_index(cpu->watchpoints, CPUWatchpoint, i); + wp = &g_array_index(wpts, CPUWatchpoint, i); if (wp->flags & mask) { - cpu_watchpoint_delete(cpu, i); + cpu_watchpoint_delete(cpu, wpts, i); } else { - i--; + i++; } - } while (cpu->watchpoints->len && i >= 0); + } while (i < wpts->len); + + rcu_update_watchpoints(cpu, wpts); + qemu_mutex_unlock(&cpu->update_debug_lock); } } @@ -945,18 +1042,6 @@ static GArray *rcu_copy_breakpoints(CPUState *cpu) return new; } -struct BreakRCU { - struct rcu_head rcu; - GArray *bkpts; -}; - -/* RCU reclaim step */ -static void rcu_free_breakpoints(struct BreakRCU *rcu_free) -{ - g_array_free(rcu_free->bkpts, false); - g_free(rcu_free); -} - /* Called with update lock held */ static void rcu_update_breakpoints(CPUState *cpu, GArray *new_bkpts) { @@ -964,9 +1049,9 @@ static void rcu_update_breakpoints(CPUState *cpu, GArray *new_bkpts) atomic_rcu_set(&cpu->breakpoints, new_bkpts); if (bpts) { - struct BreakRCU *rcu_free = g_malloc(sizeof(*rcu_free)); - rcu_free->bkpts = bpts; - call_rcu(rcu_free, rcu_free_breakpoints, rcu); + struct FreeDebugRCU *rcu_free = g_malloc(sizeof(*rcu_free)); + rcu_free->debug = bpts; + call_rcu(rcu_free, rcu_debug_free, rcu); } } @@ -2296,6 +2381,7 @@ static void check_watchpoint(int offset, int len, MemTxAttrs attrs, int flags) target_ulong pc, cs_base; target_ulong vaddr; uint32_t cpu_flags; + GArray *wpts; if (cpu->watchpoint_hit) { /* We re-entered the check after replacing the TB. Now raise @@ -2306,11 +2392,12 @@ static void check_watchpoint(int offset, int len, MemTxAttrs attrs, int flags) } vaddr = (cpu->mem_io_vaddr & TARGET_PAGE_MASK) + offset; - if (unlikely(cpu->watchpoints) && unlikely(cpu->watchpoints->len)) { + wpts = atomic_rcu_read(&cpu->watchpoints); + if (unlikely(wpts) && unlikely(wpts->len)) { CPUWatchpoint *wp; int i; - for (i = 0; i < cpu->watchpoints->len; i++) { - wp = &g_array_index(cpu->watchpoints, CPUWatchpoint, i); + for (i = 0; i < wpts->len; i++) { + wp = &g_array_index(wpts, CPUWatchpoint, i); if (cpu_watchpoint_address_matches(wp, vaddr, len) && (wp->flags & flags)) { if (flags == BP_MEM_READ) { -- 2.7.4